Just found out about this new 4X TBS under development. It's a small company in Ireland and it's still in early stages but it looks very impressive. The guy that started it is trying to make the "spiritual successor" to MOO2. It's not in beta yet but he is accepting signups for the beta. Looks very impressive so far and the TBS combat system looks very interesting. The site is done as a blog so you have to look back through the entries. There's some videos of what they have done so far. Definitely check it out. Looks like it could be good if he can pull off what he is planning.
Beta signup: http://predestinationgame.com/qcon/