some of them are getting consolidated into the megathread in an effort to keep the front page more open. i've seen devs do this before as well as volunteer community mods. you'll be able to tell if a thread got merged as for awhile it'll still be in the forum and then say Merged for its thread title. then you'll click that and it'll take you to the thread it was merged into.

if there are threads being outright deleted, that'd be lame though.