Xinjiang will be separated from China (perhaps invaded by Soviet-funded guerrilas) and KMT China will be too weak to reconquer Tibet. In addition, Stalin will not give KMT China Manchuria, so it will be an independent nation as well.
Stalin withdrew his troops from Manchuria in 1946, and I assume that the POD (not a very likely one, I'll acknowledge) is that Chiang *subsequently* wins the civil war. In that event, I do not see Stalin bringing the Red Army back. (Chiang might have been willing to concede Stalin a sphere of influence in northern Manchuria. In OTL, he declined to take Harbin, *not* as is often thought because of pressure from Marshall, but because Chiang himself did not want to provoke Stalin.
https://groups.google.com/d/msg/soc.history.what-if/gRV99OKh4jc/hMSaSkGkCeQJ)
As for Xinjiang, I think Stalin will limit himself to de facto control of the Three Districts. See my post at
https://groups.google.com/d/msg/soc.history.what-if/FnFZxyNb1uY/MbBsO1W8owAJ (The source I give there, Mark Dickens, "The Soviets in Xinjiang," is now available at
http://www.oxuscom.com/sovinxj.htm) As I note there, the Ili National Army could easily have overrun Urumchi in 1945 but Stalin held it back and brokered a compromise with Chiang instead. Dickens writes, " Why did the Soviets agree to negotiate this treaty when their puppet regime was so close to taking over the entire provincial government? One Western scholar [Andrew D. W. Forbes, *Warlords and Muslims in Chinese Central Asia: A Political History of Republican Sinkiang 1911-1949*] suggests a number of possible reasons: 'The Soviet Union had attained its primary aims in Sinkiang and had no good reason for encouraging further INA advances on Urumchi. By extending its 'all-out support' to the Ili rebels,... the Kremlin had effectively re-established its primacy in the traditionally Soviet-influenced border districts of Ili, Chuguchak and Shara Sume.' 96 This had given the USSR access to the valuable natural resources found in the area, including oil, tungsten, copper, gold, and uranium. In addition, control of the "Three Regions," as the border districts were called, 'provided the Soviet Union with an important political card which could be played both in the international theatre... and on the regional stage, where Stalin remained uncertain as to the eventual outcome of the Nationalist-Communist power struggle in China and therefore as to which side to back.' 97 Finally, 'the further the rebel forces pushed from Ili, the weaker Soviet control became over the movement.... beyond the narrow confines of the Ili Valley anti-Soviet sentiment was rife amongst the independent Kazakhs of the Altai region, and still more so amongst the traditionally conservative Muslim population of the Tarim Basin.'"
As long as Chiang does not interfere with the pro-Soviet regime in Kulja (ruling over "the Three Districts") Stalin will probably not blatantly use military force in Xinjiang or formally detach any part of the province from China. (I say "blatantly" because there was a limited Soviet military intervention at the Sino-Mongolian border in 1947, when Chiang appointed the anti-Soviet Masud Sabri as governor of Xinjiang. To quote Dickens again, "Once again, the Soviet Union, perhaps nervous about Masud's anti-Soviet stance, intervened militarily in Xinjiang affairs. This time, the area of conflict was far to the north, in the disputed region of Pei-ta-shan, a small mountain range in the still undefined Sino-Mongolian border region. This was where the Kazakhs under Osman Batur had withdrawn to after his break with the STPNLC faction in Kulja. During the summer of 1946, there had been clashes between the Kazakh nomads and MPR troops. Shortly after Masud's appointment as Governor, in June 1947, the latter, reportedly backed by Soviet planes, attacked the former. In response, Urumchi dispatched a Dungan cavalry regiment to the area. Clashes between the two sides continued until July 1948. "By maintaining indirect pressure on China in the Pei-ta-shan sector of Sinkiang... Moscow undoubtedly sought to hasten the demise of the Masud Sabri regime in Sinkiang without, however, openly breaking with the Nationalist authorities in Nanking." 102 Meanwhile, the two Xinjiangs grew further and further apart; the GMD government was increasingly controlled by Han Chinese, while the Kulja regime, dominated by Turkic Muslims and Russians, actively excluded the Han from political power.")
I also don't see why if the CCP really were totally defeated (which again I consider unlikely) China would be too weak to regain Tibet, though Chiang would presumably allow it more autonomy than Mao did.