As a serious answer, take a look at the head profile (especially the fins) and the scale pattern on the lower part of the neck. Yeah, no question, that's a mount-size 'Sormr. It was a little unclear at the reveal because of the upper neck armor (and confusion over whether it was scales or armor), but with what we know now and the fact that the name was "secret" at the time of the reveal, yeah, it's absolutely Midgardsormr. Can't wait for 2.5.2 to see how this come about.
This also means we get an entire expansion of snarky dragon commentary, don't we. :V