Mancienne came to Wolves from Chelsea primarily as a central defender but has impressed in recent months in a holding midfield role.
McCarthy is full of praise for the way Mancienne has continued to develop during two temporary spells with Wolves but will not discuss the matter until the summer.
He said: "Have there been talks to extend Mancienne's loan? No, and the reason is if someone asks me about a player I've loaned out, I'd say 'leave it until the end of the season and we'll talk to you then'.
"No-one will make any decisions on players until then.
"They (Chelsea) will want to have a look at all the reports on him from all the games like I do with mine. So I don't ask because I know the answer I'll get.
"Will Mancienne benefit from another year away from Chelsea? I've no idea. There's no point me speaking about it until the end of the season."
Mancienne has impressed McCarthy with his ability to adapt into his position just in front of the back four.
He said: "We knew he wasn't just a big head-it-and-kick-it centre-half. He went and performed that midfield role he's currently in, shoring it up for us at Tottenham to start with.
"But he's just got better and better at it. He's only just started at it but things have developed from how we were at the start of the season.
"We recognised we had to change it and he's found himself a slot there and it will be hard to move him out.
"He isn't Claude Makelele, or John Obi Mikel or Didier Deschamps - but he's someone who has gone into it and has got better at it.
"He's doing it very well for me and he's doing a terrific job."