Now that the Guardians of the Galaxy are a part of the Marvel Cinematic Universe, they're going to have to get tied into the other established Marvel properties in some way, shape, or form—that's not Thanos—at some point before Infinity War. Since we already know that the entirety of Thor: Ragnarok is going to be set off the planet earth, perhaps that's the best place to make the connection, and a new rumor is hinting at exactly that.
According to That Hashtag Show, a "source at Marvel" was able to reveal that Thor and Hulk will encounter The Cotati, the ancient plant-like species whose most famous pupil—for lack of a better word—is Mantis, being played in the upcoming Guardians of the Galaxy Vol. 2 by Pom Klementieff. According to this rumor, the Cotati will look more similar to Mantis than the stationary, telepathic plants depicted in the comics.
There is no confirmation that Klementieff will appear in Thor: Ragnarok, but at the very least this may introduce a connection between the Guardians and two of the MCU's heavy hitters. Take it all with a grain of salt for the time being, however, though it is worth mentioning that That Hashtag Show also broke the news that Finn Jones was playing Iron Fist, so they've clearly got someone on in the inside with decent info.