I doubt the Soviet Union would have been as willing to grant China licensed production of the MiG-21 fighters, or T-54 tanks to China if it wasn't for Korea. I also think an invasion of Taiwan right then would have been really costly and could have failed. Just try reading about the attempt to invade Kinmen.
In 1949, the US was still debating their strategy on Taiwan. Declassified CIA documents show that the US was caught completely flat footed by the war in Korea. The CIA was predicting instead the invasion of Yugoslavia by the Soviet Union in 1950, lol.
They had already at the time arrived to a firm conclusion that without US assistance Taiwan would fall under communist control and concluded that this would be seriously detrimental to US interests. One of the possible policies they considered was supporting Taiwanese autonomy and making Taiwan a UN protectorate. However, this was contingent on the Taiwanese being able to stage a successful rebellion, which they rated as very unlikely and therefore not pursued further.
I don’t think there was any scenario in which China invades Taiwan in 1950-1953 and the US does not intervene. This was further buttressed by US statements such as: “From the legal standpoint, Taiwan is not part of the Republic of China. Pending a Japanese peace treaty, the island remains occupied territory in which the US has proprietary interests.”
MacArthur was the loudest in voicing the critical strategic importance of Taiwan:
“The front line of the Far East Command as well as the western strategic frontier of the United States rests today on the littoral islands extending from the Aleutians through the Philippine Archipelago. Geographically and strategically Formosa is an integral part of this offshore position which in the event of hostilities can exercise a decisive degree of control of military operations along the periphery of Eastern Asia. In the event of a war United States striking forces based on this line would have the capability to interdict the limited means of communication available to the Communists and deny or materially reduce the ability of the USSR to exploit the natural resources of East and Southeast Asia. This essential capability on the part of the United States is dependent to a large degree upon the retention of Formosa by a friendly or a neutral power.”
“As a result of its geographic location and base potential, utilization of Formosa by a military power hostile to the United States may either counterbalance or overshadow the strategic importance of the central and southern flank of the United States front line position. Formosa in the hands of the Communists can be compared to an unsinkable aircraft carrier and submarine tender ideally located to accomplish Soviet offensive strategy and at the same time checkmate counteroffensive operations by United States Forces based on Okinawa and the Philippines.”
