It seems clear to me that Hasbro has no such plans at all. Hasbro doesn't make games. Hasbro SELLS games.
My secret idea as to what's going to happen: Hasbro slowly but surely lays off more and more designers and artists and writers. They only keep enough to ensure that the market has enough supplemental products to keep sales of the PHB nice and high.
At a certain point, however, the market is going to do that on its own. That was the WHOLE POINT of the SRD. Drive sales of the PHB by offloading the low-margin, high-risk work onto smaller houses. Forgotten Realms, splatbooks, adventures -- all these fall into that category and Hasbro wants out. All they want to do is turn the PHB into Monopoly -- an effortless money-maker that goes on year after year. They eventually will have NO game developers at all -- I'm sure that's their plan. That would be my plan. Zero risk, guaranteed returns.
Read Ryan Dancey's pieces on the ideas that spawned the OGL and SRD. This is what's SUPPOSED to happen. People who actually want to create game materials will be working for White Wolf, or Necromancer or Mongoose or Mystic Eye or any of the other companies already producing fine d20 material. WotC won't even exist anymore as far as D&D goes -- just that one book everyone needs to buy.
Now the market may not ever get to this point and maybe this model just won't work for RPGs. It's very interesting watching it play out, though.
Anyway, that's why I reckon there will NEVER be a 4th Edition Dungeons and Dragons.