I have seen some screenshots of Battlefield 2 and it seems fairly obvious that they took the team that created the Desert Combat mod for Battlefield 1942 and worked with them to create a full version. Another interesting observation is that while the Desert Combat mod has been around for some time, it is still in its ‘Alpha’ stage.
I am very excited to see how Battlefield 2 turns out. Battlefield Vietnam was interesting, though many fans felt that some aspects of it were ‘dumbed down’. For example, they made it simple to have a helicopter hover in Battlefield Vietnam. In the Desert Combat mod, helicopters were very challenging to fly. Some people think they should be hard to fly.
If they improve things, the biggest improvement I think they need is the radar system. Right now, the ‘radar’ in the game is very limited, and doesn’t really track things you couldn’t already see. That, and improving teamplay (APCs go unused because everyone wants to drive their OWN vehicle) are definite factors in improving the game.