His agent does not expect the 24-year-old to stay at the Stadium of Light beyond 2015 but with a series of clubs - thought to include Arsenal, Liverpool and Manchester United - circling, has suggested Sunderland may want to cash in sooner.
"I think it is very unlikely that he will sign a new contract," Nico Vaesen told the Sunderland Echo. "Simon has obviously come to a point where he wants to step up a level and there is a lot of interest in him.
"But it is maybe time to step up a level and play for a club competing for a European spot."
"He still has a two-year contract there and any interested clubs have to agree a price with Sunderland first. That is the way we conduct our business."