While I'm sure that the latter is correct, I doubt the former.
Certainly, there are a lot of 3e players who didn't want to play 4e and would have stuck with their 3e games if Pathfinder hadn't come along. But let's not pretend that there aren't gamers out there who saw Pathfinder as a legitimate alternative to 4e simply because both Pathfinder and 4e were receiving active support from the companies that created them. I know that current support is a huge deal for me as a DM, and that I give a lot of weight to playing current games rather than older games.
All that establishes that people not playing 4E had a currently supported version of 3E amongst their choices.
Your premise seems to demand that lacking a currently supported version of 3E, non-4E fans would throw their tastes out the window and play 4E.
Again, if you were right the non-PF 3E holdout would be slowly but steadily drifting into 3E. It ain't happening. If anything the net flow is the opposite direction as people decide they are done with 4E, but don't want to go to PF either.
Certainly PF has hugely benefited from the lack of enthusiasm for 4E. But that does not make the reverse true. I'm sure GURPS, Warhammer, Fantasycraft, and many others have also benefited from the market split as well. And, I'm sure that THOSE games have gained less fans because the "not 4E" crowd was their prime growth target and PF staked a big claim in that territory.
In this reality a lot of people said "I'm not interested in playing 4e." They then, later, said "I will play Pathfinder." (with a lot of people replacing Pathfinder with something else, just not 4E)
In your alternate reality with no Pathfinder the first step is unchanged. But the second step would not become "I will play that game that does not interest me." They would play other games that DID interest them. If Pathfinder disappeared tomorrow and every copy fell to dust, very few current players would go to 4E. Yes, some, but very few. Many more would go to other games. The number who would leave table top RPGs altogether would probably outnumber the 4E converts.