As reported earlier by the Wrestling Observer Newsletter, the belief among people in AEW is that Bret "The Hitman" Hart quietly signed a lucrative deal with WWE. Obviously, this means that he won't be managing FTR in AEW and it explains why he's only managing them at the upcoming Big Time Wrestling indie event.
It was also noted in the Observer that Bret has said that he plans on slowing down public appearances and autograph signings most likely at the end of this year. He is going to make exceptions for something he thinks might be a fun thing to do such as a Comic Con in Australia type of thing. Although he is allowed to do them, the decreased independent dates may serve as further confirmation that he's under a lucrative WWE deal.
It was also reported that Bret is talking about a second book on life after wrestling and what made him love wrestling as a kid.
It's unclear when the WWE deal would have been signed but it may have been recent because Bret said recently that he didn't know what he would do in AEW when asked about coming in to work there and he did not mention anything about being under a WWE deal.
There have been teases on AEW TV in recent weeks and then all of a sudden those teases stopped so that may be around the time when he signed with WWE. CM Punk and FTR have spoken about how much they look up to Bret and how they'd love to do something with him.