Jumping back to what was mentioned earlier in regards to JP and JR co-producing future DT records together, similar to how MP and JP did, I think it would fix some problems sonically, but not all the problems.
I agree that JR has seemed slightly "restrained" on the last few records, so adding him as a co-producer would certainly fix that in many ways, but it wouldn't fix the worst sonic issue (IMO) of JP produced albums: the drum sound. The fact of the matter is that when MP was co-producing, the drums sounded great, and since he has left, they haven't. Which is actually sort of funny because back when MP left my biggest concern was if DT would be able to find another great drummer that could play all of MP's parts and create great new parts on future DT music, and then found that in MM. I never even worried about the studio drum sound suffering until ADTOE was released.
So I think adding JR as a producer would help, but to solve all the sonic issues, a different engineer would need to be brought in that has a proven track record of getting great drum sounds. I actually like a lot of what Rich did on DT12, but that drum sound just doesn't work for me. Realistically though, it seems that DT was extremely happy with Rich, so if I had to guess, I'd say that he will be back at the controls for DT13...