I think that there are only three good possibilities for a "continuation" of the Rogue Squadron series (although all are more like spin-offs), and all have been mentioned in this thread.
1) A game centered on the prequal trilogy: Actually, they already did this with Battle for Naboo, but a natural follow-up to that game would be to cover episodes 2 and 3. Plus, I would
love to see Factor 5's take on the Battle of Geonosis. I'll never forget the day that I first bought my Gamecube and Rogue Leader. The Death Star level was impressive, but I'd seen it in the store. The first jaw-dropping moment that I got from my Cube however, was when I started the Battle of Hoth level. Never before in
any movie-tie in game had I
really felt like I was playing a scene from the movie. The Battle of Hoth level did that, and I think that Factor 5 could do the same to the Battle of Geonosis (and what ever is in Episode III).
2) A "Tie Squadron" game, where you fly for the Empire. Playing as the bad guys would be cool, something that "Tie Fighter" proved. Interestingly, even though that's one of the most popular Star Wars games ever, no one has ever done a follow-up to it. So just as the Rogue Squadron games are the "arcady" cousins to the X-Wing games, a "Tie Squadron" game could be the same for "Tie Fighter". You'd have to stay away from most of the movie action scenes since the Rebels always win, but they could be more like the last level in Rogue Leader where the Empire "strikes back"
3) An online multiplayer game. This was hinted at as something that Factor 5 would like to do in the EGM article about Rogue Squadron. It could be a lot of fun, especially with voice chat. Of course, as Ian has pointed out, this is something that might be best left for the next generation, but there's always room for surprises (such as this possible third party, online and
free RPG "Homeland" that PGC just reported on). I'm kind of thinking that this rumored "Battle Squadron" game might acually be this, and I really hope that it's not an X-box exclusive.
Anyway, that's my opinion. The neat thing about Star Wars is that unlike most movie tie in games, that there's enough gameplay variations that really good games can be based on it. I think though that we all agree that Factor 5 should stick to arcade flight!