The 26-year-old German, who is the son of the late F1 driver Manfred, ruled himself out of the race drive alongside Christijan Albers.
But he told racing1.de: “I have been promised that I can stay as a test driver.”
Winkelhock added that, with the scrapping of the third car rule for Fridays in 2007, he is not yet sure about how the role will be organised next year.
He drove four Fridays for the Midland-Spyker team in 2006.
Winkelhock said of the Silverstone based team: “I think (Spyker) will take a step forward in 2007. They have Ferrari engines and Mika Gascoyne and the whole crew is highly motivated.”