The Xbox Updates and Bugs forum has been lit up with problems from players ever since the update with horsies arrived. Reports are pretty varied, but as you can tell by the links above, one of the most common is repeated crashing which is barely allowing anyone to actually play the game, let alone try to get a horsey.
Luckily, the devs are on the case: “We’re aware that there have been some increased crashes after the update yesterday. The team is on the case and a fix is in the works. We’ll have this taken care of as soon as we can,” reads a recent update post. As of this writing, there is no timeframe for when this fix will arrive, so Xbox One players may need to wait a bit longer before going for their own horse friend. Until then, you can check out MJ’s latest stream to get an idea of just what mounts look like in the game.