About time we had some official word on the possibility of a new mount achievement, considering how much some people care about this aspect of the game. It is definitely worth mentioning how long it's been since the last time this type of achievement was added-- y'know, a couple of months after achievements first existed.
When that 100 mounts achievement was first added, in patch 3.0.8, it was only barely attainable at all, usually by Warlock or Paladin Engineers, or people who had spent hundreds of dollars on TCG mounts. We've come such a stupidly long way since then, and with Mists is about to add yet another metric asston of new mounts, not to mention mounts now being account-wide, a patch 5.1 equivalent to 100 mounts in 3.0.8 would probably be closer to 250 mounts than even 200.
In my opinion we need to start coaching the devs by discussing at length on the forums the most important question: whether we should get a 275 mounts achievement, or by that point just go straight from 250 to 300-- y'know, really anchor them as high as we can to make sure they don't sell us short.
Oh speaking of mounts, I need to go pick up a couple of $5 game licenses. I find having a second account useful from time to time, and I might as well get a cheap mount out of it when I next use one.
Now I need to get back to petitioning the guy who runs Warcraftmounts.com to remove Tarecgosa's Visage from the list of mounts. IT'S A SPELL, NOT A MOUNT FFS. If you're going to count spells, you also need to count Ghost Wolf and Flight Form and that thing where Kael'thas makes you fly around the room.