If BF3 ever comes out its likely to be 64 + player... meaning huge maps.... BF3 will come at some point. I would have thought it will stay true to BF2 and have all the goodness BF2 had.... I.e Jets, huge maps, 64+ players, sandbox, more server options, most custom etc etc.... personally i think all these titles BF are releasing are a way to test the market and make BF3 the biggest game on all platforms...
Think about it, if they released bf3 now they'd have huge interest... However by releasing BC2, heroes, 1943 etc it gets people more interested across the platform ready for the main title BF3...