If you shut off xp at 60 you will play in the 60-64 bracket (they have been split like this for a long time now).
I think pops are fairly sparse depending on whether you are US or EU. If you do mainly PvE compared to PvP you are probably better off sticking to level 60 for raiding. If you almost exclusively PvP you could consider going to 64.
However going to 64 may incite some hatred toward you (whether warranted or not).