Some people seem to forget that HMX is not alone in this, even if the DLC sold very well, it's not like they can say "that was great, let's do another one", "oh, I know, let's make Revolver!". They probably have to go to a meeting with Apple, decide what album they want to make, maybe Paul or someone has a different idea "Yeah, Revolver is fine, but I really want Let it Be in the game", then they have to do it, and I'm pretty sure afterwards it need approval from all the Beatles and heirs. For all we know maybe they have Revolver ready but they can't announce it, because it hasn't got Ringo's approval or something. Ringo's busy promoting his new album, and maybe he hasn't seen the dreamscapes and stuff, make sure he doesn't look weird in She Said She Said or something.
Anyway, all I'm saying is that is not up to HMX alone.