As it stands right now, the only confirmed release Dimmu Borgir has for 2017 is the Forces Of The Northern Night live CD/DVD coming out on April 14. We've been told before that a new album is definitely coming, and according to the band it most certainly is.
Dimmu Borgir took to Facebook on January 22 to announce that recording with the Schola Cantorum Choir has been completed, though a Google search of that title returns choirs from all over the world. So let's just take solace in the fact that Dimmu Borgir is finally, finally coming out with something new.