If you applied online through the FAA's job site then you will be getting an e-mail about testing. It might take a few months but they'll get around to you in time.

Also, yes current ATC is retiring the second they become able to do so. As for new controllers, there are probably a good amount that come from the military but ATC college degrees are not any real advantage. Everyone still has to take and pass the FAA AT-SAT entry testing. If you've got an ATC degree then you get to skip the first week or two at OKC which covers ATC 101 stuff.