Not so much a sequel, but rather a remake of the old Lucas Arts Star Wars DOS classics (X-Wing, TIE Fighter, Dark Forces). Heck, even just an update to run on XP/Vista would be fine with me. Would be nice to play these games again in a new engine, though.
That would be soo sweet even it they went from turn based iso to realtime FPS/third person (I really hope they don't).
A realtime third person/FPS with armor based combat in an underwater setting would be pretty unique and amazing setting and could lead to some cool effects. I can imagine seeing a topedo, missle or whatever being launched by you or a enemy and see the particle and physic effects of the topedo/missle traveling through the water at you or away from you.