One thing I would definitely see in one future expansion.
I loved it in Civ: CtP and I played the "Next War" mod in Civ IV almost exclusively,
therefore I think that you should include a big expansion of the technology tree into the future, be it with an own "future"-expansion pack, or be it with a mod in one of the expansion packs, just like the "Next War"-mod in Civ IV
(maybe the future techs should also stretch into more than just weapons technology, and allow new city and tile improvements)
I loved it in Civ: CtP and I played the "Next War" mod in Civ IV almost exclusively,
therefore I think that you should include a big expansion of the technology tree into the future, be it with an own "future"-expansion pack, or be it with a mod in one of the expansion packs, just like the "Next War"-mod in Civ IV
(maybe the future techs should also stretch into more than just weapons technology, and allow new city and tile improvements)