hmmmm AOE 4 according to the picture looks like it will be based around the WW1 + WW2 era which has been overdone extremely in both FPS and RTS, does not seem very appealing to me however AOE 5 I believe poses some more promise.
Deeply futuristic RTS has been done in games like starcraft and perhaps Tiberian sun, futuristic always leaves room for creativity because you are not restricted by fact and history.
The results could be interesting coming from ensemble as they have developed a unique style for thier RTS games and I believe futuristic hasn't been done enough in this genre.
As for the current games, AOK still reigns supreme, it had classic RTS concepts such as found in the AOE yet made gameplay easier with features such as unit key assignments which is simple and all but a major advantage over the first. The graphics were respectable and the strategy was balanced.
AOM is best described as really bad.
After playing AOE III, the demo i'm not happy but the bugs were probably dealt with in the full released, hated the american theme yet I still must play more before completely hating it.