well, for one, I would not want to see belsimtek stop making aircraft to make a map. And for two, there have been several dozen wishlist threads about a Vietnam map (I myself have made several).
And before we even make a Vietnam map, there have to be a few more aircraft like the: MiG-17/19, F-4 Phantom, A-1 skyraider, A-4 skyhawk, A-6 Intruder, AH-1 Huey Cobra, an updated B-52, and the F-105