I ran an RPGA event at an early Chicago Gameday and most of the people involved weren't RPGA members before I signed them up at the table. (Kent, did you play in that one, though as a member already?) We socialized just fine, I suppose.

William Ronald plays fairly regularly in the RPGA nowadays, I believe.
I helped run a number of RPGA Gamedays with the same fellas who run most of them around these parts now, like Mike Mensa and Brad Ruby, and I doubt it's worthwhile to go out of our way to try and add RPGA events to our own schedule. The draw of those RPGA gamedays (mostly they like to do full weekends, and cross-polinate with Wisconsin members which is a different region) is the fullness of the schedule; no matter which particular adventures your character has experienced, there's a handful more of particular ones he hasn't. RPGA members also like the opportunity to take care of out of game character business at these sanctioned events where many, many other RPGA members (and their characters, and their characters' stuff) will be at hand. So many have families and only break away for these RPGA events once every quarter. I think 6 to 8 table places pretty much have to decide to be RPGA all the way on a given day, or not.
On the other hand, if someone was an EN World regular, who regularly ran RPGA events anyway, and wanted to use the open table or two (we usually have one or two open) to pull in a group to play some offhand adventure that they had never gotten around to playing, or one that had gone unplayed at a regular COWS RPGA weekend (because a DM missed the event because she was having a baby or some other unusual circumstance) I don't see why we couldn't accomodate such a situation. I really don't think we'd ever see a situation where RPGA events would push aside other things. I think they'd want to talk to Games Plus Curt about handling a full weekend on their own if they were to do anything at all, and that's still unlikely because former Triad member Lon has a gamestore of his own (Lon's Lair) and Josh Brown who is Asst Mgr of Hobbytown, USA in Oak Park is an integral part of the RPGA events that get organized 'round these parts' (like his big, very fun, March Madness event). But those gamestores are advertised, or maybe have a booth at events because they are no where near big enough to handle (for onsite gaming) the crowds those events draw.
And to be further frank, Games Plus just isn't big enough to handle the size of events they like to organize, either. Beside the March Madness weekend, which boasts dozens of games, they combine with the College of DuPage Sci-Fi and game club to run a couple/few weekends (CodCon, etc.) every year with 20-30 tables (maybe more now!). They'll run a slot on Friday night, a few slots on Saturday and a couple more on Sunday, and gerrymander the thing in such a way as to make sure that most people in this section of the region (and from Wisconsin's region), no matter whether they can make the full weekend or just a day, will have as much gaming as they can cram in without having slots that their character can't find an adventure. It's very well organized and they really are more like mini-conventions than the casual day we put together.
They also combine with the Highfolk gang (Wisconsin) to organize some on the south end of their state (which allows for that many more adventures, since some are region-specific, that folks from this region or that can play in. As you can see one of the drives of RPGA members is to manage to pack as few weekends as possible with as much gaming as possible so that their character can run through all of the national adventures, and all of your regional adventures in a year, and for those lucky few who can organize at the border between two strong regions like WI and IL/IN, you can run your PC through the regional adventures of a bordering region as well. Of course another goal for RPGA members is to sustain their characters and adventure with others in an ongoing, shared world. It's designed to be inclusively-cliquish, if that makes sense.
And money changes hands for their events, which might further complicate things for Chicago Gamedays. Obviously the guys who set these big events up like to make sure that they not only have their expenses covered, but that they will wind up not having to pay out of pocket for their own gaming (a much deserved perk for some very dedicated workers). Plus, there's the whole prize thing. IIRC, the RPGA events have very limited prizes, if any, because the character advancement is sorta the reward.
Anyway, I don't think RPGA games at Chicago Gamedays is a good idea or a bad idea, just (realistically) an unlikely integration. We're small potatos to them.

I hope my overview of the RPGA from my limited perspective didn't bore or offend anyone, but I think it's fairly accurate. Nevertheless, it it wouldn't be the first time I was wrong, so who knows?
