Hmm. well i would think a general sequel would be a lot easier to make at this point than both RA and Tib.
They already have all the generals 2 assets ready, they just need to whip up a story, polish the game a bit and it's all good to go lol.
The model's themselfs aren't SCI-FI enough for Tib series. Lore wise they pretty much destroyed the Tib story with CnC4, plus they concluded the tib story with kane's ascension and Left GDI with total control of earth.
Problem with RA series is that RA overall theme is very toony, and the generals 2 model would look very awkward compare to the lRA2 and RA3, since they are a bit more realistic looking. so they have to build everything from ground up again which i don't see why they would left all the good assets to waste.
Generals hasn't had a proper sequel in over 10 years plus it's almost the 20th anniversary or Command and Conquer franchise. generals is essentially a blank piece of paper it would be a good fresh reboot of Command and Conquer.