Jones was doomed the moment Belichick left. And with a QB heavy draft, Mayo likely wants to start fresh with someone to build the team around. What happened in New England was not all on him, a lot of it was Belichick changing schemes seemingly at random even though everything was mostly clicking. And just simply not getting the right support around Jones. It was obvious that the team has had doubts about him since that first year.
Maybe in Jacksonville some of the pressure will be off and Jones will have more time to develop since he will be coming in as a backup rather than the lead guy.