I'm curious what you feel general applications need? I come from a games background and am in current heavy R&D for VR and AR applications. I tend to feel VR is much more like a game than anything else. You're fundamentally working in 3D space with tracked game controllers in a simulation that updates at 60/90/120Hz. Most of what's lacking for common application development is the sort of things we won't see until there are some mature VR/AR operating systems. AR in particular really needs to allow multiple programs to run simultaneously. There's not really the need for that with multiple overlapping virtual realities right now.

I don't think Unity necessarily has things wrapped up but it would be really hard to eclipse them right now.