In canon timeline During the reign of Shapur II, the Sasanian Empire and the Kushano-Sasanians gradually lost the control of Bactria to these invaders from Central Asia, first the Kidarites from around 335 CE, then the Alchon Huns from around 370 CE, who would follow up with the invasion of India a century later, and lastly the Hephthalites from around 450 CE. It is not so in this timeline, Gupta are intact and all the centre for Buddhist scholarship flourishing.
In canon due to huns Indian urban culture was left in decline. Major traditional cities, such as Kausambi and probably Ujjain were in ruins, Vidisha and Mathura fell into decline. Buddhism, gravely weakened by the destruction of monasteries and the killing of monks, started to collapse. Great centers of learning were destroyed, such as the city of Taxila, bringing cultural regression. The art of Mathura suffered greatly from the destructions brought by the Hunas, as did the art of Gandhara in the northwest, and both schools of art were nearly wiped out under the rule of the Huna Mihirakula. New cities arose from these destructions, such as Dashapura, Kanyakubja, Sthaneshvara, Valabhi and Shripura.
Soon after the invasions, the Gupta Empire, already weakened by these invasions and the rise of local rulers, ended as well. Following the invasions, northern India was left in disarray, with numerous smaller Indian powers emerging after the crumbling of the Guptas. Many autonomous regional states rose to prominence following the dislocation of Gupta power: the Aulikaras, the Maukharis, the Maitrakas, the Kalacuris or the Vardhanas, all in a constant flux of rivalry.
The Huna invasions are said to have seriously damaged India's trade with Europe and Central Asia, particularly Indo-Roman trade relations, which the Gupta Empire had greatly benefited from. The Guptas had been exporting numerous luxury products such as silk, leather goods, fur, iron products, ivory, pearl and pepper from centers such as Nasik, Paithan, Pataliputra and Benares. The Huna invasion disrupted these trade relations and the tax revenues that came with them.
So I think without white huns gupta will continue to expand further and remain intact. Buddhism remain strong contender against Hinduism and we will a north india dominated by buddhism and Hinduism rather than christianity.