I'm always a fan of worldbuilding stuff. The "Roll your own dungeon" from 1e DMG is freakin awesome. I wouldn't say they should repeat that, but something along those lines would be pretty cool. Lot's of tables for worldbuilding/geography/towns/landscapes/and dungeons. Maybe it's asking too much, but I think it would be awesome to be able to build at least an entire region from dungeons, to towns/cities, to environments, etc all from rolling via tables. One could argue that you could just pull that stuff from older books, but if you're new to D&D and pick up the new DMG, how much would that fuel your imagination!?