Penny Arcade nicely sums up why D&D5 won't be the game saver that Hasbro wants it to be; Not enough players and too many expectations. I'm not sure why, but WotC seemed to have pissed away most, if not all the goodwill they generated with the release of D&D3 and the open source rules. It will be interesting to see if they can get it back (and if so, how). I think the worst case scenario right now be if D&D5 flops, Hasbro gives up on tabletop D&D entirely, but sits on the name for DDO, boardgames and figurines.
Nevertheless, D&D has certainly risen from the ashes before and the tabletop hobby will always have its players if only because, like me they have not been particularly thrilled with their MMO experiences.
My suggestion for WotC is online support; kind of a Google+ system specifically for running tabletop D&D. And if they are really smart, make it backwards compatable for all editions.
But if TWINKIES are having trouble making money, then who knows what the future brings?