Latecomer to the thread.
I did want to pop in and say that I was at DragonCon and had access to a lot of their gaming data. 4th Edition did indeed have a presence there, but only in the form of the RPGA. No "open" games of 4th Edition were running. Also, their RPGA numbers were down this year, while their Pathfinder Society tables sold out.
As far as the animosity between the editions...I can vouch the same thing. I encountered it anecdotally numerous times throughout the convention. People denigrating 4th Edition, etc, etc.
As others have said, this is has nothing to do with how well either of those two games are doing. It indicates neither success nor failure with either game. It does mean that 4th Edition does not seem to be popular with the "DragonCon" crowd.
One thing that a lot of the RPGA organizers speculated is that most of the Living Forgotten Realms games now are being played at home. This is (according to them) killing small, regional gaming conventions. If this is true, I think it would be rather sad. One awesome thing about the advent of 3rd Edition and the RPGA at that time was the explosion of small conventions and the opportunity to meet other gamers from around the country. That said, I have no idea what a good solution would be. Allowing RPGA games to be played at home is great and necessary. But it would be nice if we could give people who went to conventions some kind of carrot.