We don't know whether he's actually signed a contract of if this is just a temporary partnership with Ring of Honor, but Jeff Cobb showed up on AEW Dynamite tonight and is scheduled to take on Jon Moxley on next week's show.
Chris Jericho announced that he'd hired Cobb as a mercenary to teach Mox a lesson, making the match for next Wednesday. Jeff then showed up in the final segment of the episode, delivering his Tour of the Islands finisher to The Purveyor of Violence and standing tall with The Inner Circle.
Cobb is set to challenge Jay Lethal and Jonathan Gresham for their ROH tag-titles along with partner Dan Maff in the near future, so we know he hasn't signed exclusively with AEW. Hopefully we'll get some more details next week.