Ancelotti fostered a relationship with Ronaldo during their time together at the Santiago Bernabeu But believes a reunion is unlikely.
The Italian says the Portugal captain wouldn't leave the Champions League holders even if Bayern were to make an offer.
"I love Ronaldo's professional attitude," Ancelotti said.
"Journalists often ask me how difficult it is to work with players like him and Zlatan Ibrahimovic, but it is really easy. You don't have to tell these kinds of players anything. They are very disciplined and focused.
"Something can always happen in football, but it is very hard to see a player like Ronaldo at another club.
"The same goes for players like [Lionel] Messi, [Philipp] Lahm, [Thomas] Muller and [Paolo] Maldini, who played his entire career at Milan. Players like them simply cannot leave their clubs. They care too much about the clubs the play for."