So, do what do you think WotC did to D&D?
The OP seems kind of caught up in...technicalities.
WotC added a "core system" to D&D (d20 + mods vs. a DC) that was easy to understand and intuitive. Then they flipped the D&D rules as they existed to revolve around this core system. This was their big Game Design change, and it drove many (though not all) of 3e's changes.
This happened to be financially successful as well. This could be for any one of a number of reasons, somewhat related to the core system innovation, or not. Consumers are not entities driven by a cold dispassionate logic, so logic won't tell you what's going to succeed and what won't and why.
The success of 3e's fairly extensive revolutions set the stage for more big changes in 4e, and arguably 4e has been relatively less successful (not that it hasn't been a success, just that the 3e -> 4e transition is probably less successful financially than the 2e -> 3e transition). Again, this could be for hundreds of petty and half-mad reasons.
If WotC had never acquired the game, I don't think we'd have more editions. I think we'd still have the retroclones, but I don't think anybody would've picked up the d20 system and the OGL and ran with them, and the retroclones would necessarily be niche fan projects (probably smaller than the audience for OSRIC or whatever today). It's possible that someone at some point would dredge up the old title and try to re-purpose it for a "new generation," but it would probably bear even less resemblance to 2e than 3e did.
I think that WotC acquiring the licence was overall a good thing. They threw Pokemon Money at the game, gave it room to grow, and gave it the OGL, which enabled, and still enables, a flowering of awesomeness. The alternative to me seems to be small fan projects that remain closer to 2e, different RPGs, and possibly a re-launch that bears little resemblance to the original. I think we're living in a better world than that, at the moment.
