These are my alt-4e speculations. They carry about as much weight as "What would 19th century US history look like if Lincoln hadn't been assassinated", i.e. no predictive weight at all. This is just idle thoughts.
1) I think if the 3.5 Vancian casting structure had been imported to casters (i.e. what Bo9s did), but casters had been left alone, the amount of concern around it would have been heavily muted.
2) I think releasing a 3rd core rulebook set in 8 years was a poor decision to allow for a positive reception, even if the economic need was urgent and pressing.
3) I think even if WotC had released the exact rules of Pathfinder as "4e", it would not have been successful because it was "too similar", and again, few people saw the need for a 3rd core rule book set in only 8 years.
4) I think there existed a sweet spot of changes between the "mostly the same" PF and "very experimental" 4e, that would have done better than either, if it has been released as "4e" in 2008. I don't what that exact sweet spot is, and I don't think it's identifiable now, but I think it definitely existed.