He's already said that multiple times this year, and most of the beat writers have also reported as much. He just happened to give an interview to Bob Nightengale where he said it again last week.
They will probably announce his extension at the same time as the permanent new managerial hire (regardless of who that is), and on the same contractual timeline (so, 2028 or 2029 depending how long they give the manager, though if that's on the short side DD's deal might be longer).
The only other question is whether they will explicity anoint Mattingly as successor. And if not, if he'll accept interview requests for PBO jobs with other teams.
Philsmania has also suggested several times that he might get a piece of the team along with it, but I kind of doubt that, especially with the larger new ownership structure. I do wonder if Gillick's share returns to the team on his passing (unlike Monty's).
