Yea, I think that they only will support the standard PBEM, and PBEM with simultaneous turns played by a host.
I have played tons of SE3 multiplayer games, and yea, sometimes was frustrating try to finish a game... because some people is so lazy to play their turns fast (although, have played some fast games through ICQ).
To speed up the multiplayer games, in the old SE3, they did a feature into the setup game (that I hope that they finally include in SE4), to start with some tech, (not all the tech, because it's less interesting).
In my opinion (ok, only my opinion), a multiplayer game like MOO2 (turn based), or Pax Imperia 2 (real time), or BOF (turn based with time limits), is not very useful into the SE series.
For example: how do you expect to test the enemy ship designs in the combat simulator, if also, you must look the clock?
Anyway, would had better for them, included this feature to get a more wide market...