The Dutchman has agreed to join Norwich at the end of the season.
Agent Louis Laros told A Bola: "There is a special clause in the deal accepted by all parties that stipulates if Norwich leave the Premier League then the future of Ricky van Wolfswinkel will be open again.
"That is the reality, but we are confident in the ability of the English club to remain in the top division.
"For now Ricky is only thinking about Sporting and helping them to get results. At the end of the season he will start to focus on Norwich."