Looks like development on the reboot seems to be progressing smoothly because 3D Realms is already gearing up to host a closed test for this shooter, and guess what. You can join the test, too.
So, if you're one of those who want to be among the first to jump into a beautiful demon-slaying experience, the closed testing is scheduled between June 4 and June 16. That's quite a stretch of time to see what the new Painkiller has to offer.
Anyone can apply, but it does not mean that he or she will form part of the testers. Likely, the test will choose people among applicants. This phase of testing appears to be technical-focused-take it as a pressure test of the systems, most prominently in anything affecting multiplayer.
Participants will have to sign an NDA (Non-Disclosure Agreement), which is pretty standard for these tests. Of course, a few leaks are expected in the gaming world; however, officially, nothing is meant to be known.
For everyone else who does not get accepted into the test, there will still be the full release. And if everything goes as planned, we might get to see the Painkiller reboot releasing sometime in fall. Fingers crossed.