Chris Taylor, the designer of Supreme Commander, has previously said that current hardware is too limited for his vision of Supcom 2
WTF - even more performance consumption for a title that doesn't really run fluent on today's hardware?
I'd sure like another SupCom (not that there would be much like it anyway it would have to stand against and no - Starcraft II doesn't belong to this list). I'd just like it to be more "complete" than SupCom. In the end we have 4 nearly identical factions with different Experimentals and some advantages (imo it's like UEF=slightly better air, Aeon=slightly better sea, Cybran=slightly better ground units). With FA we then got the imo superfluous Seraphim race which was a waste of work imho. Not only that they changed the race concept from some kind of greenish aliens (-> Intro) to Cyber-Apes speaking jabberish but you also got an entirely new faction with even more units which have to find some room in your computer's memory. Instead of doing that I'd have prefered if they finally filled the gaps in the Tech-Trees like some T3 mobile ground-AA, some underwater buildings etc. - pretty much what the Core Contingency did to TA...
Story-wise SupCom imo was ok - the focus is on the gameplay just like TA and in comparison SupCom really has a way better story. The FA continuation was ok too although the ending really was the lamest thing they could possibly come up with...
So yeah - why not another one? I'd either switch or change the "universe" a bit to have less races which on a wide scale just have different looks for their units...