I like to think the Knights were the Autobot equivalent of Seekers being ancient explorers. Knights of Cybertron without it being said. Since the Seekers used to work for the Primes looking for stars to harvest guess that makes them Star Seekers? Makes you wonder what sort of relationship Grimlock and his crew had with Jetfire and the other four Seekers. Maybe they were rivals? Or even enemies of each other. Being legendary of each of their sides.
Pretty sure if any new Transformers villains are arriving it will be the Creators... Which begs the question of how they can be pre-Autobot yet have Decepticon symbols as shown by Jetfire, as Autobots and Decepticons were founded at the same time.
I gotta say with the poor continuity we have seen so far odds are we'll probably never even hear about the Knights in the next film.
Nah they weren't founded the same time. The original faction of Transformers was Cybertronian. The Fallen rebelled and founded the Decepticons. Cybertronian civilization fell to the point their only recorded history is within the Allspark. Most of the Dynasty of Primes, the leadership of Cybertron dead. From the ashes the Autobots rose rebuilding civilization. The Fallen and his Decepticons forgotten. The Fallen seduces Megatron to the dark side resulting to a revolt that became the second generation of Decepticons. AOE presents us with some missing piece in this story. Namely who opposed the Decepticons when the 6 Primes were gone? The Knights of Cybertron being legendary warriors means they have fought numerous battles. As Lockdown notes they are crusaders. Optimus being a Knight also gives a plausible reason how he escaped the Fallen's purge of his brothers. The Knights took him in away from the Fallen's reach.
Yeah Jetfire would tell so much about it Seekers maybe was good warriors too, not so mighty but faster. But possibly they have different functions. Why do you think that Knights must be space explorers?
Interesting that Slug has an Autobot symbol. More fuel for my theory the Dinobot Knights were the equivalent of Seekers.