I've said it before here, I firmly believe the lack of good modern subjects is hurting the cause. If the premise was to get the aircraft guys to occasionally cross over, then they [the manufacturers] are leaving out a whole lot of jet builders to start with. The new HMMWV is a tepid start I think.
Purely from a choices point-of-view, the non-WWII modeler hasn't had any chance to help sales and I for one would love to see T-55, -72s, M-1s and M-60s, Challengers, Chieftains, Centurions, Strykers etc., etc. from all our favorites. The aftermarket has already proven they can supply the detail and conversion sets and are willing. The data is already there so I am honestly confused by some the production choices made in the last 2 years.
Until you get the across-the-board proliferation of subjects to include all markets (or at least the major ones) then the sales will continue to slowly decline. Unless Dragon or Trumpeter/Hobby Boss reintroduce themselves to 1/48, I don't see this happening any time soon--at least not with us relying solely on Tamiya's shoulders with minor help from Italeri & ICM (and not in the way I'd hope it would have happened like with the Blitz, which doesn't look like the superior Tamiya release in 1/35).