I think both Dybdal and Mr Banners are right. He's talking to his family and he's leaving for Austin's freshman year.
Austin might be one and done, but I guess Doc could be out of coaching for a couple of seasons, helping his kid to make transition. He probably will do some broadcasting while at it, and after that he'll go back to coaching.
By then, I'd say the Celtics are his #1 option, and it will depend on the Celtics coaching situation. If all the above is true, the Celtics need a HC next season. They could go with Frank, or they could go with another ex-player as a HC, with Frank and other high-character assistants. They could even hire Jerry Sloan, or another veteran if they win it all this year and they're going on a last dance with their veterans.
Next season (if there's a season) Danny will make big trades, or little trades, or prepare the team for a big FA signing in 2012 or 2013. Ray and KG could be back in limited roles for little money, or they could be gone at the previous trade deadline. Whatever route Danny chooses, in the summer of 2013 the Celtics will have a totally new lineup, and that's when Doc could be needed the most. By then, of course, the Celtics could have a successful coach and no need for a new one, but I find it hard to think Danny has not Doc included in his plans.
Doc is a true Celtic, he's friends with Danny, and he wouldn't go to be Pat Riley's pet. But if he wants to coach another team, I'm fine with it unless it's the Fakers.