Everyone. It's a laptop replacement.
Realistically this "Pro" version is for early adopters. There will surely be a regular/SE/Lite version in a couple of years for the price of a MacBook Air.
> And who will develop software for something with such a small user base?
Everyone will, if they're smart. Being first to market on a new platform is huge, even if it will take a few years to have significant market penetration.
Angry Birds became a multi-billion dollar franchise for being one of the first iPhone games. Who knows what the equivalent will be for XR.