Tony Vargas
Legend
That's an indisputable correlation, yes. Furthermore, it's part of a pattern - every new ed (even half-eds like 3.5) stirred up resentment and nerd rage and lost some fraction of the current fan-base as people stuck with the old edition. The lack of any ongoing support, though, made the hold-out communities less than vibrant.The evidence is pretty overwhelming - I find it galling that anybody could seriously argue that all the issues we have been quite angrily debating about for years on this site and elsewhere have not, in fact, stemmed from the release of 4e. That's what all the arguments have been about - for or against!
4e contributed to the edition wars simply by existing. What 4e was didn't matter - that is, the direction it took wasn't the issue, the issue was simply that it wasn't 3.5 (which inevitably enraged some grognards somewhere, as with every rev-roll). The fact that 4e wasn't under the OGL, also contributed (again, the content of 4e was irrelevant, just the fact that it wasn't OGL), because that gave 3pps a stark choice to support one of the other.
Paizo saw the backlash, was able to tap it as a market thanks to the OGL (something that had never before been possible in earlier rev-rolls), and 3.5 holdout community had something to rally behind besides old books.
So, yeah, 4e was part of it, but it wasn't the real cause, just a trigger that was inevitably going to happen eventually.
Those factors led to the division in the community coming out in the edition wars, but they didn't create the division, they just brought it into the open. Two not-too-distinct groups of D&D fans who'd been kinda vaguely putting up with eachother all this time finally had different places to go.
The distinction is one that's hard to characterize in a polite way, but lets just say it's deeper than 'style' or 'preference,' and goes to how players relate to eachother and the role the mechanics of the game play in that relationship. I think the end result is that, in spite of the on-line vitriol, 3.5 fans are happier playing Pathfinder than they were playing 3.5 with 4e-fans-to-be before the split, and 4e fans are happier playing 4e than they were playing 3.5 with Pathfinder-fans-to-be before the split. That is, to the extent that the two factions hadn't already divided themselves group-by-group.