I’m just doing a project at work (engineering consultancy) reviewing different gearbox / drive systems for bikes. We have come to the conclusion that there is a reason that chains have been used for so long and will continue to be. They are cheap have good efficiency and allow for a lot of misalignment. Geared systems need comparativly high levels of accuracy in their machining and mounting. Plus you get issues with most of the load being taken by one tooth. This is why planetary gears are used, so the load is shared by more teeth. Yes you could make the gears from stronger material (and case harden it), but then it needs refinishing due to distortion. The cost of gears goes up and up, compared to bits of stamped out steel.
Systems like the Pinion may be very good for a few bespoke manufacturers, but until the big boys (i.e Giant) start making thousands of bikes that use systems like it, the humble BB and chain/deraileur system will continue to be used.
The Alfine system will start to be used more and more I think, and having it linked to a belt drive does make sense to me.