As far as I know the epic flyers aren't changing prices anyway. The only thing is you may receive a small faction discount if you were exalted. So the difference is minimal. You might as well get your epics now and make gold faster from doing faster dailies and what not. The only significant cost changes are for those that don't have riding up thru 225. So if you haven't gotten a normal flyer and wanted to wait or an epic ground mount and wanted to wait.

If all your waiting for is epic flying then get it. It will be worth it.