I agree it cuts out the very low end, but there are a ton of people left that have either dedicated or nearly dedicated (e.g. road legal but never really used for anything else).
The lowest end of the hobby will change, obviously. Not convinced it will completely go away. I think my point was it isn't a crazy bump in expense to have a vehicle you play with only on the track, though it may not be the same vehicle.
And yes, it means you can't easily drive your hobby car out to a drag strip to see what it will do. Or a bunch of other things. But it doesn't mean there is no hobby to be had - at least I hope so.
4x4 is interesting, i hadn't considered but suspect that will be under more pressure than track days.