The Danish international is currently nearing the end of a season-long loan deal from Arsenal.
However, the striker has confessed that the odds are against him playing for either club ahead of the new campaign.
"Never say never about Sunderland, but it is not certain that I will be here if the opportunity arises," he told Sporten.
"About Arsenal, I obviously have to have a chat with the club about [the future], but it's not there that the first priority is going to be. I think I have been fairly clear about it."
The 24-year-old has scored seven league goals for the Black Cats.