I will put my two cents' worth (or less):
I think that at the Frankfurt Musicmesse Roland will begin releasing info about the next instruments, with the actual products available in the US sometime after Summer NAMM. It has been over two years since G1000 was released and this seems to be about the length of the Roland (and Yamaha) product cycle. Also, some posts in this forum have reported that G1000, though not yet discontinued, is not being sold by Roland dealers anymore. A local retailer here in Phoenix is trying to sell an EM2000 at a greater discount than they normally offer (for $2000).
At NAMM Roland seemed to be more secretive than everybody else (they had no arranger keyboards shown in the general display areas, but they had a separate room with more keyboards cordoned off for authorized dealers only). I would not be surprised if they had shown something there with a non-disclosure agreement and a threat of being chopped into sushi. With some G1000/EM2000 remaining in dealers' stock, I can see how Roland would want the news of their replacement kept very low key. Japanese companies are known for very tight product management.