Firstly I just found the LOMAC site, I was lamenting the fact that Flight simulation was dead, and then, Eureka! I absolutely can't wait for this game to come out.
Realistically I think that the F/A18 E/F and the S-37 or perhaps Mig 1.41 should be the next ones to come out, as the represent the most modern fighters from each side. Someone did make the point that more flight models means less quality. I would not like to see the quality of the sim degrades by quantity of planes. I would rather pay more fore more planes, but most other people probably wouldn't so I can't see massive numbers of planes being developed.
Perhaps they could relase the F-15E with the S-34 under the rule of thumb that all planes must have counterparts.