Probably yeah. It's hard to tell with emerging technologies, because sometimes they take off and it's really awesome to have been on the ground floor, and sometimes they flop and you just have to pick something else.
And yes, when you focus, it does reduce the pool of possible jobs. However, it tends to reduce the pool of competing applicants even more. You might not fit the profile for job A or B, but somewhere out there is company C, and they're desperate for workers.
The one thing to watch out for is to make sure you specialize in something you enjoy working in. Otherwise, you'll hate it, and chances are all that effort will be lost. If you don't know what you enjoy working in, it's fine to try lots of areas until you find one. But if you do find it, don't be afraid to go deep.
And yes, when you focus, it does reduce the pool of possible jobs. However, it tends to reduce the pool of competing applicants even more. You might not fit the profile for job A or B, but somewhere out there is company C, and they're desperate for workers.
The one thing to watch out for is to make sure you specialize in something you enjoy working in. Otherwise, you'll hate it, and chances are all that effort will be lost. If you don't know what you enjoy working in, it's fine to try lots of areas until you find one. But if you do find it, don't be afraid to go deep.