I noticed a few months back that the Servo engine (upon which I was building a play/experimental browser) development had shifted significantly in the direction of Mixed Reality (it shifted more than a few months back, but I was not paying that close of attention). At that point I gave up on my browser project.

Some execs at Mozilla think MR is the wave of the future. I think it's mostly a party trick with a very niche market and will always only be a niche market, and wasting top talent on MR seriously detracts from a project that is a hundred-fold more important. But maybe that's just me.