Well either way Drew is going to NXT. He confirmed it in an interview after the show.
I think there are a couple things at play for Galloway in NXT.
First is WWE want to sign him before anyone else could, especially with how the UK is very hot and getting a show on national free TV in prime time on a major channel. And there are a couple other promotions on smaller channels too. He'd be a key guy for any company, gotta take him out of play. We've gone back to the late 70s, early 80s over here lol. WWE buying up all the talent. If you even look slightly British they'll throw a contract offer at you atm.
Second is they probably don't have a sport for him on the main roster, especially not right after 'Mania with call up and other signings. You can only give people so many new things at once, so he'd be lost in the shuffle a bit. So keep him on NXT as a star in the meantime. Also builds more buzz about him.
A bunch of us have been watching him in TNA and the indies and know he's improved a ton (he was actually good before he left WWE, but he was already dead at that point so it didn't matter), but a lot haven't. NXT gives the WWE smarks a chance to see him again before debuting. It's basically a pre-wash before the re-debut.
Or he could just be on a Rhyno/Joe/Roode deal. Or he could be fully signed and end up there for years lol. What ever it is, he's Galloway and awesome. Great that more people will see him again.