I agree we'll see OT and maybe even PT stuff into the future in some measure, but the speed at which they're going through the major costume variants of Han and Luke and Imperial troops in the 5 POA line tells you everything. By the time TFA hits, Hasbro will have done all of them, leaving nothing to cover. The same is happening in the 6 inch line, though the release schedule on those is so slow that I'm wondering if we'll see the Emperor by the time the movie toys drop.
Yeah, I don't see a very long shelf life for the 6" line personally. You can only afford and have space for so many of the larger scale... the major characters are going to dry up quickly and how many people are going to buy $20 obscure figures that take up three times the space of the ones they've been collecting for years?