eagle-eyed Joseph Browning has found confirmation that, yes, we will be getting another AD&D rulebook reprinted -- Unearthed Arcana in February 2013.
The choice of Unearthed Arcana is a strange one, given the relatively low regard in which it's held by most old schoolers. On the other hand, it carries Gary's byline (even though it contains work by others) and, unlike Monster Manual II, which is also by Gygax, it's player-oriented. Plus, the original Unearthed Arcana was renowned for the shoddiness of both its editing and its binding. If the reprint corrects both those issues, it'd go some way toward making it a more attractive buy.
I'd still rather that WotC reprint something like the LBBs or Moldvay/Cook, but I'm not going to complain about seeing more AD&D on the shelves of game stores. If anything, it suggests that the original batch of reprints must have sold decently enough. I can't imagine WotC would bother with a follow-up volume if the previous release had been a bust.