This is my concern. I think these changes coming in 5.2 are great for the games arena/pvp community, but one of the major incentives of reaching 2200 rating was not only for the increase in stats, but also the cosmetic rewards. WoW, like most MMO's, is about chasing that carrot on a stick and I do hope they remember to roll out new cosmetic rewards with this pvp overhaul.
I am actually really surprised they made this announcement today without also including the new cosmetic rewards they have planned for the PvP community. Near the beginning of Mists of Pandaria, I believe it was Cory Stockton, who mentioned their goal was to introduce more cosmetic rewards and a larger variety of them at some point in the future for the pvp community. I think that information should have at least been mentioned today along with these changes to make the whole announcement a lot more digestible.
Anyways I think this change is great & I hope this gives Blizzard the flexibility now to start rewarding some really creative cosmetic items. This is anecdotal, but one of the reasons I believe arena in BC had more participants, who were also particpating at a higher frequency, was because rewards were incremental (1000, 1500, 1750, 2000, etc.). Compare that to now where the only milestone is 2,200 and to the casual player that might as well be 3000. I hope they bring back that tiered reward structure with this change.