Check out this guide to know which characters and Pokemon will become new Sync Pairs in Pokemon Masters. Also includes Sync Pair assumptions and more!
Table of Contents
Announced New Sync Pair
Blue & Pigeot Joining on Sept. 3

Once the Pokemon League Champion in Kanto, Blue joins the team with Pidgeot by his side! Cut down all opponents in the battlefield with their Air Cutter Sync Move.
Unlock Blue in Reach for the Top Story Event

Blue will be part of the Reach for the Top Story Event. It's a limited time event that will only be available from Sept. 2, 2019 to Sept. 29, 2019.
Possible Sync Pairs to Come
Cynthia & Garchomp

There's a good chance that Sinnoh Pokemon League Champion, Cynthia will become a Sync Partner in Pokemon Masters seeing as she's part of the Official Website.
Steven & Metagross

Hoenn's Champion Steven could also join as a Sync Pair. He's even featured in the Pokemon Masters' official cover art work and was featured along with Metagross in the trailer.
Other Possible Sync Pairs

Giovanni & Persian | Lance & Dragonite |
Maxie & Groudon | Archie & Kyogre |
Diantha & Gardevoir | Molayne & Klefki |
Jasmine & Steelix | Elesa & Zebstrika |
Ghetsis & Hydreigon | Lysandre & Pyroar |
Guzma & Golisopod | - |