It's been forever and I didn't recall any, but your mention of possibly skipping issues (which I guess could be fill-ins, but again...) made me think I was forgetting something. If they don't collect the entire run I'm going to throw such a tantrum. I've wanted this to get collected forever and never thought there was any chance.
The only acceptable excuse would be if they decided to release an Absolute instead. Give J'onn the treatment he deserves!
still no announcement of a third volume. was the second one the last?
No word on a third Martian Manhunter volume yet. Or a third Spectre.
I haven't given up hope yet, though. It's a bit of a consolation that there are new volumes of Dixon's Nightwing and Grell's Green Arrow on the horizon...
vol 1 and 2 of spectre sold over 1k, which is quite ok for this kind of cult classic collection with no big creators attached. i'm still hopeful we'll get a vol3 but the whole run finished in tpbs? probably not.
DC hasn't listed their end of the year tpbs schedule yet. Current schedule only reaches August/early September. It seems like the plan was to release two volumes of MM and Spectre a year, so I'd expect something around September/October for both series if they're going to continue. (I'd also assume that the first tpb of the new MM series will be early next year, so they'd probably push things back until April or May on the Ostrander series for a fourth volume (again, if they're continuing).
Classic Hellblazer releases have been the best gauge, and they've been roughly on a 6 month release schedule.