You'd be surprised what can be tracked with just a headset. There's an app on Steam that I absolutely love called "VRocker". It has two modes it can process movement through. One has you shift your weight left and right, and it converts that into forward movement, feeling kind of like a slow lazy walk at low speeds, or roller-skating at high speeds. The other works in a similar way to a pedometer, tracking the up and down jostling when you run in place, and converts that into forward movement in VR. You have to spend a couple minutes the very first time you run it, to calibrate the sensitivity and movement speed into what feels the most comfortable for you personally, but it works like a charm. Plus, the body movement you're doing helps eliminate motion sickness from moving in VR. VRocker itself can hook into pretty much any game out there, letting you implement the physical movement system into games like Skyrim or Fallout, even. (It can also stack with VorpX, as well.)
I'd assume that mimicking a similar system would be incredibly easy for a big AAA company to do. Jog in place to run, shift weight to walk. If they were to implement something like that, San Andreas VR could be an amazingly immersive open world game, which to be honest, VR really needs. The biggest-scale games we've got are still HL:Alyx, Skyrim, and Fallout, maybe Alien: Isolation if you want to include the VR mod. You don't even see Vivecraft very often anymore, unless you're watching one of those ultra-realism shader show-off videos. We've got the tech at this point, we just need a couple decent developers to help give VR a kick in the pants to get things going. (HL:Alyx came pretty damned close, though. A couple more releases at that scale would have done the trick.)
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