There are a bunch of new mounts on the way--maybe some are related to new mount achievements?
Would love atleast a 125 one, sitting on 132 myself, would be something nice to work toward.
I'd like to see both a 125 and a 150 added. Though my main/mount collector isn't at the 125 point yet, it would at least give me something to work for instead of just randomly farming mounts when I feel like it.
I'm pretty sure they'll eventually update this achievement with a 125 and 150 count. I'm still farming semi-rare, uncool mounts just in case! (VoA and such)