Bill Murray seems to have singlehandedly brought down any hope for a Ghostbusters sequel starring members of the original cast. However, he ain’t afraid of no reboot—particularly one with an all female cast.
According to The Hollywood Reporter, Bill Murray will appear in the film, though there is no word on what is role will be. He follows Dan Ackroyd who also agreed to make an appearance.
My guess is that they will appear as their original Ghostbusters characters for a brief cameo, perhaps to give their blessing to a new franchise. This would make sense if the plan was to create a Ghostbusters universe with different teams (while maintaining a connection with the original). As you’ve probably heard, there has been lots of talk about a movie featuring a new male-led Ghostbusters team, though that project appears to be in limbo at the moment.