It was specified that you can't have 2 accounts. For all intents and purposes though, it looks like they are one program. All points/elite night credits/and status can be switched back and forth at any time. The only difference is that your communications will come from RC if you enrolled in that program, and MR if you are enrolled in that program.
Edit to add: three are still some questions outstanding regarding the treatment of RC stays / RC enrollment for promotion treatment (like the Megabonus), as well as the counting towards LT status. It seems like the concensus is to stay with MR until we know more.