So as of today I've visited two local game conventions in two consecutive weekends. Last weekend I was in Bloomington, IL for FlatCon and today I went to Springfield for a taste of I-Con. Both of these are small local conventions with attendance in maybe the hundreds.
At Flat-Con the role-playing section was dominated by the RPGA, with Living Greyhawk 3.5 events winding down the campaign and Living Forgotten Realms well-attended. I talked to one active RPGA friend who boths DMs and plays that said a lot of people he knew were making the switch of both campaign setting and game edition with little difficulty. And my informant was really digging LFR's crazy new campaign rules.
Meanwhile, the roleplaying in Springfield was dominated by Pathfinder, with a smattering of other 3.5 events. Not a single 4E game was scheduled for the weekend. In fact, if you wanted to play an rpg besides 3.5, your choices were a single game of Dark Heresy (the new 40K rpg, right?) and All Flesh Must Be Eaten. And those games were running at the same time, so you couldn't play both.
I found it pretty dang weird that these two cons would be so polarized like that. The towns they're in are only like an hour's drive apart.