From what I've read in random bits and pieces so far:
A) The rest of Priest has made clear they will welcome back KK if he wants to return.
B) Nostradamus was released as a group effort. If all didn't think it was good to release, including their label, it wouldn't have been released.
C) If KK decides to write ballads for Justin Bieber, he's still more metal than JD Diamond and Head banger in both current lives and past re encarnations combined.