Huth has not featured for the first team since sustaining a knee injury in November which led to him having surgery.
He played 45 minutes of a behind-closed-doors friendly on February 25, but is yet to return to the Potters' matchday squad.
And Coates, quoted by The Sentinel, said: "It is my understanding that it is very unlikely he will feature again this season.
"If that is the case, then all the focus now is getting him ready for next season."
Huth has missed 20 matches in all competitions since limping off in Stoke's 2-0 home Barclays Premier League win over Sunderland on November 23.
Marc Wilson has been playing at centre-half in the German's absence, and Coates added: "It will be good to have him (Huth) available again because, along with Ryan Shawcross and Asmir Begovic, he has long been part of the backbone of our team.
"But the fact we have done so well without him is a tribute to the team in general and to Marc Wilson in particular."
Stoke are six points clear of the relegation zone in 12th place with nine games left to go this term.