Assuming you're all caught up on the quest, yes! You should be able to get your legendary cloak
pretty quickly once Patch 5.4 hits.
The reasoning is simple: we want you to be able to use it for progression. Past legendaries (including the earlier bits of the Mists of Pandaria chain) have typically taken a pretty decent amount of time before you're able to get them. That's great for heading into the next tier (or finishing up the current one), but when the next tier is in a new expansion, it can leave them feeling a little... flat. You end up using them mostly for farm, and then you replace them once the next expansion hits and you outlevel them.
It also feels a little strange thematically. "We need to properly gear you for the fight against the Lich King so uh... go kill the Lich King!" Bit awkward, but required for gameplay purposes. A legendary doesn't feel terribly legendary if there's no effort involved in obtaining it.
So, since you've been working so closely with Wrathion over the course of the expansion already, it makes sense that he'd want to equip you properly for the final resolution of the Alliance vs Horde conflict -- before you set foot in Orgrimmar. And since you've put in so much effort up til this point (starting in patch 5.0 and continuing up through patch 5.3), we don't really need to add more.
We've obviously been experimenting a bit with how players earn legendaries in this expansion, so continued feedback (both on how you earn them as well as the actual legendary items themselves) is extremely valuable. Thanks!
We actually have an alternate proc in the works for Hunters, we just weren't able to get it ready in time for this PTR push. Giving you the melee proc off of your pets was just a temporary measure :)