I live in the Bay Area and I’ve seen a surprising number of them. But then again I think their R&D office is in a nearby city so maybe it’s just a bunch of employees driving them.

Enough that there will still be some available. If hydrogen becomes unavailable then the car's values drop to almost zero regardless of how many there are.

edit: California Energy Comission reports that there were a hair under 12,000 hydrogen fuel-cell vehicles operating in California in 2023

I think that Toyota recently announced they sold a total of 14,000 (in the US, I’m assuming). They also announced that they were planning on continuing production on the same article, but I don’t know what this will do to their plans.

First of all, there are three (popular) hydrogen cars available, and only one of them is from Toyota. And more are scheduled to launch very soon.

Everyone who's tested those three cars loves them. The Toyota Mirai is supposedly very similar to, and in fact nicer than, the Lexus LS 500 and it's also tens of thousands of dollars cheaper than that car. When (and I believe it is a "when") hydrogen is easier to access, it's going to take off.

The only real drawback Hydrogen ever had was cost. But that's not an issue anymore, prices have come down a lot. And the "range anxiety" issue is helped tremendously by just having a really really long range. You're only going to fill up twice a month or so.