It's really hard to answer that question as Roland usually keeps the secret until just a few weeks or even days before a new release.
But I heard they're still manufacturing the RD 2000 so it is not discontinued. You will know that something is coming when the RD2000 gets discontinued, but not yet.
It is interesting that the RD2000 has taken longer time in the market than other releases from Roland and other brands. But I think it's because of the fact that this piano was setting new future standards (like having an integrated audio interface, the new rainfall technology which will replace MIDI in the future, and take in mind that the RD2000 is marketed as a digital stage piano but it is actually more than that, it is a master keyboard/controller).
I strongly believe that all they need to do is to release a system update for the RD2000 with new sounds and features and more expansion capabilities, plus a couple of new Axial expansion libraries. And keep adding to the keyboard. But I don't think they wiould do that. The business is to make us buy a new instrument which is more profitable to them when the time comes.