It's fairly split on popularity from what I can tell. A new RM dividing the existing fan base isn't a surprise though. I don't see it being much more or less successful than the move from RM2 to RMSS or RMSS to RMFRP. A portion of the existing customer base is essentially lost each time. Those who are lost may want bits and pieces of the new one, but they'll never fully buy into it.
I think it's all going to hinge on how well you've customized your own RM, if you see value in switching and if you like the changes.
Personally I don't like most of the major changes myself and, unfortunately, enough fundamental mechanics have been altered as to make back-converting things problematic.