I think they will restrict it at first, to control the user experience. In the starting phase it'll be crucial to avoid bad reviews due to substandard hardware. Google did exactly this with their cardboard headset. People lost interest in VR because they watched a rollercoaster vid on a crappy cardboard setup and thought they had seen it all. All these $5 eBay headsets flooding the world didn't promote VR at all. They just imprinted the idea "VR is just a gimmick" in people's minds. As a VR enthusiast I still need to explain the difference between 3DOF and real interactive 6DOF all the time. It took a long time to build interest in real 6DOF VR back up.

But I think once (or, if) the metaverse has proven its value to the consumer their goal is to be the leading platform and opening it up would make sense there, it would be key to maximising marketshare. Especially as they're not even making money on the hardware, it's being sold at a loss. That'll change too once the platform proves itself but still I don't think they expect it to be a major money maker.

Zuckerberg mentioned in his keynote that they want to go for a different business model. They want to sell the platform and enable creators to sell their designs, taking a cut in the Apple store way. And they can still take a cut on third party hardware by licensing. Which means revenue without even having to bother manufacturing anything.

I think hardware to Meta will be what hardware is to Microsoft. Setting a good baseline standard, promoting new designs and usecases (e.g. the surface pro convertible) and directing the market. But not being the sole vendor.

But I may be wrong of course. It'll be interesting times ahead!