You won't have 8 hours of battery life with such displays and computing power, I think, unless the battery is huge - hence the rumor about a belt-attached battery.I think it's inevitable that VR/AR becomes a very large market. Maybe not smartphone big, but at least laptop big. But that's only if there's not some fundamental technical issues that make it impossible to create wide FOV with sharp optics across the full FOV, 8K+ per eye, lightweight/comfortable, all with 8+ hours battery life.
Most current headsets aren't good enough to be comfortably used with most non-VR apps. But once the technology gets to a certain level, VR will become a feasible alternative to a flat screen device for more and more people.
That said, I hope it also has controllers, so many of the already great VR apps can be ported over.
On the controller topic, I'm not an expert but I'm pretty sure devs will find it easy to adapt their controller-based game/app to an eye-tracking system. Apple will make it easy for them. Or it just won't care cuz only very few people actually have a VR headset as of now.