One thing to keep in mind is just how unpopular Truman was by 1952. Almost everything that hurt Truman's reputation by that point occured in his second term. By 1952 he might be much more popular than he historically was in 1952-or than he was for some time after he left office historically.
Presuming Truman is not personally blamed for the loss I can see him being rehabilitated much faster.
That's a part of this. How would the 1948 Republican victory be interpreted?
Would the view be that the Democrats were inevitably going to lose-since they had held the White House for 16 years by that point.
Would the defeat be blamed on Henry Wallace?
Would the defeat be blamed on Strom Thurmond's Dixiecrats-and thereby make Democrats wary to offend the South again on the issue of Civil Rights?
Would Truman himself be viewed as being responsible for his own defeat? That is are there decisions he made as President or during the campaign that would retrospectively explain the loss-even in a popular vote electoral vote mix match scenario?