Simultaneous. Even though it could be VERY buggy, if Firaxis does it right, it will be awesome.
I don't trust turnless, for some reason. I just have an intuition. The idea of taking a turn-based game and making it turnless seems potentially disasterous to me. I don't think PBEM will catch on, b/c no one wants to email someone a thousand times. I don't think hotseat will ever catch on.
I won't play multi that much, stick to SGs.
Why? I can play 5 SGs at the same time, only devoted maybe 15 minutes to each. But multiplayer, that is a two, three hour commitment, even with turnless.
What I want is classic multiplayer, only with people who have the same schedule as me, so we can all play half-an-hour a day. Of course, that will never happen.
CG