I'm very well versed in PPC assembly. I've found a quite wonderful niche working on automotive controllers. I also have several subordinates well versed in Tricore (Infineon automotive CPU) assembly.
Neither of those will ever make it onto any list of "popular" anything, but we all make plenty of money doing it.
As important as those two languages are to what we do, I've never hired anyone that listed either of those things on their resume. The ones that did list them specifically had at best a rudimentary understanding and little other practical background that would make them useful.
Don't learn something because you think you can make money with it. Learn something because you like it and want to use it. Then, find an employer that values your talents and willingness to learn whatever they need you to learn.
That's the best path to a good paying job.