In an absolute sense, this is true. There are never likely to be hundreds of thousands of compiler jobs.
In a relative sense, this isn't true. I run a PL research group with a heavy focus on (mostly dynamic) compilers, and I've lost track of the number of companies (some obvious, some not) who are desperate to hire people with a compiler background to do compiler stuff. Because there are so few people with suitable training, and as said elsewhere on this thread, industry has become used to taking good people without a compiler background and crossing their fingers that they can learn the ropes -- which good people of course can, given a bit of time. But, in my experience, even groups which are largely staffed with people who haven't done a compiler PhD would love to hire people with compiler PhDs.
Will this always be true? Well, it perhaps wasn't (as) true 15-20 years ago when people often only seemed to care about C++ and Java performance. But, given the continual increase in the quantity of languages that people want to run fast (and, often, on a variety of devices), it's hard to see that happening any time soon.