You'll be missing out on 2 Diamond choice benefits if you don't qualify this year.
If you expect to get to 125K MQM's (without rollover) by the end of next year (or very close to it), and you think you will likely maintain that pace, I would just go for Diamond now. If, however, you think you'll likely come up short of that mark by a decent amount, the rollover plan might be better.
this +1, skymiles program isn't getting any better so i would say re-qualify for DM this year and hold your breath and see what will come in 2016, at least you will have 4 GUCs in your pocket and 25k miles or GM to gift someone instead of just 4 RUCs for PM.