This is in a spirit of fun. I'm looking forward to the new creative team, with a bit of trepidation. Here's a few ideas I'm pretty sure would've been passed up when deciding the fate of our favorite superteam...
--LEGION OF SHADOW PUPPETS... FORESHADOW (this continuity's UMBRA/SHADOW LASS) goes to the 'Bah!' side. She gets the 'cloud of ancestors' power-boost, but instead of rejoining the Legion, she takes them over. One by one, her ancestors absorb the Legionnaires until they're under Foreshadow's control.
Once she's conquered the Legion, Foreshadow realizes she doesn't really want to be a villainess, so she sets up business doing shadow puppet shows in public parks... occassionally saving a galaxy here and there by trotting out the puppets under her control.
LEGION OF FURBALLS... STREAKZZY the WIZCAT aided generations of wizards on Xerox. He got tired of the 'familiar' and embarked upon his own quest for power. That quest led to a duel with Mordru. Streakzzy catscratched the old wizard and Mordru died. But before he took his last breath, Mordru cursed Streakzzy... limiting his magical prowess to that of the 'hairball' spell.
Streakzzy coughs up a hairball, bats it into a victim's face and gains complete and total mastery over that entity until Streakzzy decides to release them. Guess who his targets are... Streakzzy bears a grudge towards the Legion after viewing their 'oppression' of metabeasts in a magic mirror. (Streakz had taken a roll in catnip the day that alternate realities were covered in mirroire class, so he's a bit confused.)
LEGION OF ROBOTS... Robotica won. Thom and Jenny are actually robots who 'upgrade' their teammates one by one.
GORILLA LEGION... Gorilla World (a colony of Earth's Gorilla City, *not* a theme park) forms its own superteam.