My latest check with Remington about the reintroduction and got this response from them on 10/23/15:
We appreciate your patience as we continue our efforts to re-launch the R51. Currently we don't have a time frame for the re-introduction but our Huntsville R&D center is working to have it back on the market as soon as possible.
Hello SPRic and thanks for signing up and for the update on the R51.
Robert