Patch Notes are up!

[Shougun]

I don't recall them saying that all Primal Mounts will fly, only that Kirin will be able to fly.

I've never had the chance to quote myself before so I had to lol, the news is recent, someone else also had the question you had :P

Unless it was accidental wording, "Ahriman and Bomb mount (from Kobolds) as well as primal horses will all fly. First one to fly will be Kirin.". Source.

Kirin will be the first, but all primal horses will at some point fly (although "first" was phrased with a question mark lol). Sleipnir would technically be a primal horse.

[Ultimatecalibur]

I've never had the chance to quote myself before so I had to lol, news is recent someone else also had the question you had :P

Direct 2nd party (i.e. from SE US staff) info trumps a 4th party (reader) translation of a 3rd party (online magazine) interview.

[Evergrey]

I've never had the chance to quote myself before so I had to lol, the news is recent, someone else also had the question you had :P

Ok, well it would fit the norse mythology that Sleipnir can fly. Still misses 4 legs though (Sleipnir has 8 in the mythology).