Hopefully they left on good terms, I would think so anyway. I have had people leave me and go to other trainers and end up coming back. There is nothing wrong with that or trying to go it on your own for a while. By now I would think that Dexter has the plan down pat. Joe is very good at getting guys lean. He does seem to at times, have trouble peaking guys for the day of the show. This is not a slam against Joe, just the way I see it.
In order for Dexter to hold on to the Olympia title he is going to have to put on another 5 to 7 pounds. This is good amount for a guy like him and he also has to return to that shredded conditioning that he has brought in before that set him apart from the other guys. Combine these two things together and he will retain that title next year.