Campbell has impressed in the Championship for the Tractor Boys so far this season and scored his seventh and eighth goals for Town while on loan in the 3-0 win over Millwall on Saturday.
He does not appear to have much of a future at Loftus Road and is way down the pecking order. McCarthy has confirmed the much-travelled striker does want to stay on at Portman Road beyond his current loan spell, which ends in January, although the boss admits there could be interest in him from elsewhere due to his good goalscoring form.
"They [other clubs] will have all noticed DJ scoring goals here but there is nothing we can do about that," the Town boss told the Club website.
"All we can do is try and do a deal with him. He wants to stay long term at a club and I think this club would be his first choice, with things starting to go better.
"But there are a lot of mitigating circumstances that can change that situation."