I think some simplification of the written language would have occurred, much like in Japan with the Kyuujitai, but would they have done some things differently?
How would the spoken and written standards develop? The Qing Dynasty used a koiné as far as I know called "Guanhua" 官话 frequently called "Mandarin" in English. This standard was closer to Late Middle Chinese than modern Standard Chinese and preserved more initials and vowel distinctions.
Generally, it's usually a bad idea in linguistics to confuse spoken language with written language, and it's particularly true in the case of Chinese.
*On one hand, the traditional written language (文言,
wényán) was a form of Old Chinese that had its own conventions and all that, nowadays called Literary Chinese or Classical Chinese. For most of the 20th century, when Westerners have their stereotypical views of Chinese, and especially Chinese characters, they are usually referring to Classical Chinese without realizing it. Classical Chinese was to Imperial China what Classical/Modern Standard Arabic was to the Arab world or, until the 18th century, Church Slavonic to Russians, or, until the 19th century, Latin for Western Europe. There was a form of Mandarin that tried to reflect the vernacular speech of the Ming and Qing dynasties (白話,
báihuà), but until the formation of the ROC was largely limited to novels and other similar "low-brow" literature.
*On the other hand, there's the spoken language (what in linguistics has been gradually shifting to calling Sinitic instead of Chinese, a small change of wording that tried to better describe the speech varieties spoken in Greater China and the Chinatowns as if it was a language family) in all its diversity. Again, for most of the 20th century, Westerners generally have their stereotypical views of Chinese either based on Cantonese (or Taishanese in North America) and archaically-Romanized versions of Mandarin based on both the Nanjing dialect and the archaic speech of Beijing opera. This is when it gets tricky, because - among other things - the English word "Mandarin" refers to both Northern varieties of Chinese (hence "Modern Standard Mandarin" instead of "Standard Chinese" is preferred among linguists in recent years) and the language of the Qing court and administration. Now, it is true that it was called 官話/
guānhuà, but in actuality it was not close to Late Middle Chinese; rather, the original basis of the language of the Ming and early Qing court and administration was actually the Nanjing dialect of Mandarin, which indeed preserved some vowel distinctions lost in the Beijing dialect (which increasingly became the base of the late Qing court and administration, although Nanjing-based literary pronunciations were still considered desirable) because Nanjing dialect was in contact with other Southern Chinese varieties, most notably Wu Chinese (aka Shanghaiese). This was also the target speech of baihua literature, but outside of the confines of the Qing court and Northern China, other Chinese varieties continued to evolve on their own.
A persistent trend here (and one that confuses speech and writing) is the coexistence of literary and colloquial pronunciations. Colloquial pronunciations refer to how people actually spoke, except when incorporating loanwords from other languages (which was becoming a thing around the late Qing, especially from Japanese and European languages) or using references from Classical Chinese, when literary pronunciations were used. These literary pronunciations often reflect prestigious speech from another city (for example, literary pronunciations in Taishanese tended to traditionally reflect Standard Cantonese, the prestigious speech of Guangzhou) or, indeed, reflecting distinct reflexes of Middle Chinese (the latter was especially true of Literary Southern Min, which was a highly-developed system shared on both sides of the Taiwan Strait until the Japanese colonization of Taiwan in 1898 and the formation of the PRC in 1949).
Now, if somehow the Qing dynasty maintained power with a post-1900 POD, how would spoken and written Sinitic develop over time? Let's just say it would be very complicated.
*The Qing court, around 1909-1910, was starting to develop a national language standard (國語/
guóyû) based on the court speech, but the Xinhai Revolution scuttled plans to carry those plans any further - not to mention hampering plans to reconstruct China's educational system after the abolition in 1905 of the Imperial examinations (which formed part of the base of increasing the number of people who learned the Confucian classics, and hence of people able to fluently read and write in Classical Chinese). That paved the way for the formation of Modern Written Chinese (which, although notionally based on Mandarin speech and especially a continuation of the traditional baihua of the Ming and Qing dynasties, also contained within it a lot of translation-ese from European languages and a considerable amount of influence from Wu Chinese), but it could have evolved differently.
*It could be possible to have a similar language situation (if European languages are discounted) to modern India, where other southern Chinese varieties could be promoted to standard languages and co-exist with Standard Mandarin (much like how Marathi, Bengali, Tamil, etc. coexist with Hindi-Urdu). That would be a big boon for Cantonese and Hokkien, the two major non-Mandarin varieties of Sinitic which were more than capable of having standard languages based on the speech of Guangzhou and Amoy, respectively, but it also could provide a positive impact for Teochew, Hakka, (Old) Xiang, and several others. Thus, at least a few myths about Chinese writing could be shattered, especially if regional calligraphic styles are adopted (i.e.
for Cantonese) and/or each standard written language selectively simplifies characters differently and/or different variant characters are adopted.
*At the same time, it could be possible to come up with a different evolution of Standard Mandarin, based on the 1909 edict that the Imperial court speech was the national language of the country. It was certainly possible, on the written side, to modernize Literary Chinese to accommodate baihua within a Classical Chinese-oriented writing system (for the most part, Hu Shih's guidelines about literature reform could be just as helpful with modernized wenyan as it would to later Modern Written Chinese IOTL), alongside its accommodation of Japanese and European loanwords. That should help cut down some of the translation-ese that is a hallmark of OTL Modern Written Chinese; to some degree, this could also be used by other non-Mandarin standard Sinitic varieties as a base from which to develop standard written languages of their own. Standard Mandarin pronunciation could therefore be sharply divided in its literary and colloquial pronunciation, based on historic factors:
>Literary pronunciation (i.e. loanwords and Classical Chinese, among a few other things) could come close to
OTL Old National Pronunciation; while its ad-hoc and artificial nature would make it sound a bit weird (particularly the three additional initials, which did not exist in Nanjing dialect but they do in regional Mandarin, such as
in Sichuan), it does come the closest to what during the Qing dynasty people considered to be desirable Nanjing-based literary pronunciations
>Colloquial pronunciation, by contrast, would be more similar to what we know IOTL today as Standard Mandarin pronunciation, with the only real colloquial dialect to make it to the standard language could be the full voicing of <b, d, g> /p, t, k/ to [b, d, g] (plus a few others like <j> (Pinyin: <zh>/<j>) /ʈ͡ʂ/ [ʈ͡ʂ]-[t͡ɕ], for example, which can go straight to [d͡ʐ]-[d͡ʑ] instead of actual dialectal [j]), especially in unstressed syllables but could be possible in stressed syllables as well.
I could go on, but I have other prior commitments I need to address, so I'll leave it there. But even here, that should give some idea of what I'm thinking it could go.
Also, modern Chinese lacks honourifics besides the occasional use of "nin" 您 instead of "ni" 你. Would we see more formal vocabulary?
Only if retains Classical Chinese as the main language and/or borrowing honorifics from Japanese (which, considering a lot of those borrowing happened during the Meiji period, would be definitely understandable why Chinese people would borrow from Japanese to address lexical gaps).
