Disney has yet to announce the stand alone Star Wars movies that they are currently developing. The only movies that have been officially announced at this point are Star Wars: Episode VII, VIII, and IX. I think we all knew deep down that one of these spin-off films would involve the bounty hunter Boba Fett.
In a recent interview with AMC Movie Talk, Metalocalypse director Jon Schnepp basically confirms that a Boba Fett solo movie is in the works, and that Empire Strike Back scribe Lawrence Kasdan is the one writing the script for it! The director seems pretty sure of himself too saying,
"One of them is Boba Fett. It is. I know. I know for a fact. I will never reveal my source, but it is the one written by Lawrence Kasdan."
Until we hear anything official, lets treat this as a rumor, but at the same time it does make perfect sense that Kasdan would be writing a Boba Fett movie. Now if they could only get Boba Fett creator Joe Johnston to direct the movie! That would be amazing! I'd be disappointed if Lucasfilm didn't at least approach him about it.