Not hotter loads, necessarily, but heavier/longer bullets. The heavier/longer a bullet is, the more inertia it has and the more it resists spinning. This necessitates a tighter twist so you can put more spin on the bullet to stabilize it well enough to fly well. The plus to these heavier/longer bullets is that they stay stable longer and have better flight characteristics. When bullets in the 70+ gr are used, a 1:9 twist usually won't stabilize them enough for consistent accuracy.
If you never shoot more than 69 gr bullets then a 1:8 and 1:7 twist barrel give you nothing... but it won't hurt anything you shoot, either ("overstabilizing" = myth). If you do shoot heavier bullets, or plan to, then you'll be better served with a tighter twist barrel. Competition shooters like heavier/longer bullets, and arguably the best LE duty loads in 5.56x45 are 75-77 grs.
Bushmaster had the perfect opportunity to get 1:7 barrels exactly like those Remington is getting, but still chose to do their own thing seemingly "just because". I'm not so confident Bushmaster will be offering 1:7 barrels. I'm not even confident they'll offer SBR assemblies or the Remington aluminum lowers. Here's hoping I'm wrong.
-B