Noone, 29, has made 170 appearances for the Bluebirds since joining from Brighton for £1m in 2012.
But he has struggled to secure a regular first-team place recently and Cardiff could sell him before his contract expires in 2018.
"I think Nooney realises it's time for him to move on," said Warnock.
"I think he needs a new challenge now. He's done ever so well for the club since he's been here.
"I only ever played two years at a club and I was a winger and I was ready to move on, and I think Craig needs a new challenge, get his enthusiasm back."
Another Cardiff winger, Anthony Pilkington, could also be on his way out of the club.
The 28-year-old signed a two-year contract extension last September, keeping him at Cardiff City Stadium until 2019.
But Warnock says the Republic of Ireland international could be among those to depart this summer.
"Pilks is similar [to Noone]," he told BBC Wales Sport.
"Pilks can score more goals, but whether he needs a new challenge or not, that is something which will be discussed in pre-season."
While Pilkington and Noone's futures remain undecided for now, one player who seems destined for the exit is left-back John.
The 21-year-old has started only one game for Cardiff since Warnock was appointed manager of the Championship club in October.
"I think Declan will move on," the 68-year-old said.
"I had a good chat with him last season. I think the time has come for him to try his luck somewhere else.
"He's a little bit stale with us, he's not going to get much of a look in. I look at the left-back and left forward positions and he's kind of in between in the Championship.
"I think he could do a job somewhere and I think he's got to be playing now. I'm not going to stop him."
Cardiff City winger Craig Noone and left-back Declan John are likely to leave this summer, according to the club's manager Neil Warnock.