Considering that Wallace remained a Democrat until his death in 1998, I don't think he would ever become a Republican.
If Thurmond "stole his thunder" Wallace still would have had plenty of chances to switch to the GOP in the 1970s and 1980s
According to this article, George Wallace switched over to the Republican Party in the early 1990s (due to dissatisfaction with the growing social liberalism within the Democratic Party) and voted for George H.W. Bush in 1996 and Bob Dole in 1996. I also feel that if George Wallace lived for another 20 years and remained somewhat active in politics, he would have strongly supported Donald Trump and approved of the populist direction that the Republican Party is currently taking.
I've often thought that it would be frightening if Wallace in his prime was alive today and able to make use of Fox, Breitbart, etc. He was a ruthless politician, intelligent, charismatic, and a spellbinding speaker. Picture a competent and focused equivalent of Trump in the White House.
