I highly doubt we will see a windfall of things released. Reason being is that it costs money to put these things out, and whoever pays for it expects a reasonable return. Every type of release has a cost associated with it.
So here are things that I think are likely from most to least:
1) New 'best of' package. This one would be more comprehensive than Thank You. Dead and Bloated would be on it, the single version of Creep, Meatplow, Pretty Penny, Unglued, Tumble in the Rough, Hollywood Bitch, Wonderful, etc...maybe not ALL of the songs played on radio, but more than Thank You. Of course it will also include stuff from self-titled, including Between the Lines, Cinnamon, maybe Take a Load Off. Maybe they will finally use the title, "Big Bang Babies." If no b-sides album is planned, I could see them putting some of the unreleased tracks listed below on this release, maybe has a double disc.
2) A b-sides/loose songs/rarities album. Could even include old demos. Only Dying, Super Scary Area, Fast As I Can, You Can't Drive Me Away, Heed the Water Whisperer, About a Fool, Samba Nova, Way She Moves, Watchin' You, Dancing Days (full version), Revolution, Break on Through. Also Sheer Heart Attack and Where Do The Children Play (if they exist), and any other unreleased songs that are complete or mostly complete.
3) A Blu Ray/DVD concert. My best guess would be the August 1999 MGD Blind Date concert in Vegas in full. The band seems to think this was one of their best. Also, some SLDD concerts were recorded professionally, including one I went to back in '01 or '02 at the Joint in Vegas. One of those could be released.
4) A documentary. As we know from Thank You, there is lots of footage of them recording their albums, lots of bootleg footage (remember they asked us to submit what we had when that came out) except possibly No. 4 and self-titled. I could see, instead of the SLDD doc being released, that being folded into a more macro concept of a history of the band, with new interviews with the guys, Brendan O'Brien, other musicians, other guys who worked on the albums, etc.
I could also see these being released in some sort of combination with each other. I doubt we get all four though.