It's a concussion. They keep saying it's not a concussion but Meltzer and Alvarez are saying it's a concussion and they're keeping it a secret because they're being sued. The big problem is Bryan worked a couple days of the tour after the fact and that would be a BIG BIG BIG BIG BIG blow to a judicial case. Bryan will probably stay away until that case is settled.
No, I don't believe his long term career is in doubt. If it were, WWE wouldn't be constantly reminding you that he's gone and might never return. When he was away last year, they stopped bringing him up for weeks at a time because they legitimately didn't know when he would be cleared. I think they have a pretty good idea when Bryan will be back, but it may not be until early August.