The Quarterly issues and Returns are supposed to be like ~50 pages each, so between that and the last 10 of the regular run you're up to 500 pages at least. Then you have the second Question Annual, which is also a multipart story with the Green Arrow annual, and the Question shows up in Green Arrow Annual #3, all of which are ~40 pages each, so that brings up to 620 or so.I'm wondering what they'll put in it. Volume 1 ended with issue 27 of a 37 issue run. The Question Quarterly is about 5 issues, The Question Returns just 1 issue. After that it's stuff written by other writers. I've read Rick Veitch's mini series which was incoherent gibberish so I hope they don't include that. No idea what Lemire's run is like.
I read the rest of O'Neil's run online and there was a small dip in quality but it picks up again ending with a fantastic last issue and panel.
If I were to guess, they'd fill it out with the Lemire Black Label book, since that was drawn by Cowan at least. But they could also do the Veitch run. There's probably some other random Question stories they could fill things out with.