Interesting. VERY interesting....
One big hiccup is gonna be Ferrari's relationship with the FIA and Ecclestone. (I assume he is the source of this problem like just about every other problem in Formula One?)
The 2010 field (I'm assuming this is 2010, F1 was in no danger of problems in 2013) aside from Ferrari included Red Bull, Mercedes, Lotus, McLaren, Renault, Sauber, Williams, Force India, Scuderia Toro Rosso, Caterham, HRT and Virgin. You already mentioned Williams, and with Whitmarsh being the announcer of the move it makes McLaren part of the GPTA. HRT, Lotus and Virgin were new to the sport and so don't really matter all that much, but where do the others fall? Sauber and Force India are GPTA locks. Red Bull and Scuderia Toro Rosso probably would also side with the GPTA. Mercedes and Renault are wild cards, particularly the former - Mercedes management is more likely to side with the FIA, but the minority investor in the team and Ross Brawn himself are more likely to side with the GPTA. Toyota and BMW were on the way out, and Toyota MIGHT be able to be kept if you can get their management to try to use F1 as a national pride deal after the Tohuku Earthquake, but that's pushing it and endurance racing works better for Toyota's environmental image. BMW's gone, and they aren't likely to come back after their 2009 season was as poor as it was, and the fact that BMW had been in F1 for a decade and had but a handful of wins to show for a $2 Billion+ effort. (This is why BMW prefers now to race touring and GT cars.)
And if F1 breaks into two series, you need a lot more cars on the grid from some place. Where do you get these? USF1 is out of the question (it's gone by now). Prodrive and Epsilon Euskandi siding with the GPTA means they are on that side, too. Of GP2 teams, DAMS, Carlin and ART are probably capable of F1 entries if the possibility was there. Sports car aces Ray Mallock Limited wanted in as well (they could probably make it), as did Italian touring car racers N.Technology (these guys, probably not), but both bailed out during the FIA-FOTA crisis. In 2010 Indycar teams are out of the question aside from maybe Team Penske (and that one is a stretch), and of the sports car world I can only see Rebellion Racing, Onroak Automotive and Strakka Racing finding F1 as a possibility (and the latter is gonna need help, but they are Dome Cars were working on Le Mans Prototype chassis at the time, so that might work). It's hard to find good teams to fill up a grid on either side.