If they were ever going to extend NXT's timeslot, then maybe they could go to 90mins. Don't try to shoehorn in any more storylines though, just give some of the matches and wrestlers a few extra minutes to do their stuff. They could use the extra few minutes in a bunch of places not just matches though. Sometimes I feel entrances are rushed, with the likes of Balor and Asuka racing to the ring, when they have entrances that I dont mind lasting a minute longer. Backstage segments could get a few extra minutes too. All those minutes would add up and fill the time, and make the show feel less rushed.
Of course with the way they do NXT tapings, adding 30 mins to each NXT episode extends the tapings about 2 hours longer, so it is probbaly a bad idea in the long run as most crowds would get burned out at that point.