Day 1-2

Team Rainbow Rocket has made their debut! In Celebration of 20 years of pokemon they have brought back all the big pokemon villains and they all join the Ultimate Team Rainbow Rocket!
Giovanni is the Leader of Team Rocket in Generation 1 which is the first pokemon games. (Red, Blue, Green(JP), and Yellow.)

Team Rainbow Rocket Grunts

In addition to Giovanni Returning his grunts also get a colorful reappearance!

Team Aqua Leader Archie

Archie has made his return to be a Team Rainbow Rocket member! Notice: It is based off the original Archie rather than the Gen 3 remakes. Archie is the Leader of Team Aqua in Generation 3. (Ruby, Sapphire, and Emerald.)

Team Magma Leader Maxie

Maxie has made his return to be another Team Rainbow Rocket Member. Notice: This is the original Maxie from Gen 3. (No Glasses.) Maxie is the Leader of Team Magma in Generation 3 (Ruby, Sapphire, and Emerald.) and is a Rival to Archie although in the trailer they are working together in the same group which is odd for two people with complete opposite ideals.

Team Galactic Leader Cyrus

Cyrus has also made his return to be another member to Team Rainbow Rocket. Cyrus is the Leader of Team Galactic in Generation 4. (Diamond, Pearl, and Platinum.)

Team Plasma Leader Ghetsis

Ghetsis has made his return as well to be yet another member to Team Rainbow Rocket. Notice: This is the original Ghetsis from Black and White and not from Black 2 and White 2. Ghetsis is the Leader of Team Plasma in Generation 5. (Black, White, Black 2, and White 2)

Team Flare Leader Lysandre

Lysandre had made his return to be a member of Team Rainbow Rocket as well. Lysandre is the Leader of Team Flare in Generation 6. (X and Y)

That is a lot of returning bosses! From Gen 1 to Gen 6 it will be the most feared evil team yet.
I can't wait for Ultra Sun and Ultra Moon. Why are all these evil Leaders returning? Why are Ghetsis, Maxie, and Archie in their Original outfits rather than their new or their updated ones? Well, I guess we will have to wait and see. Well that's all I got for now so keep on theorizing and getting hyped for USUM!