We reported last month that F2 driver Natacha Gachnang, who is Buemi's first cousin, has been in talks with the new-for-2010 F1 entrant Campos.
It has been speculated that a test contract with the Swiss 21-year-old is a possibility.
But on a visit to a Swiss kart circuit, Toro Rosso's Buemi, the only rookie on the formula one grid this year, said he will only believe new teams are entering the sport when he sees them in Melbourne next March.
Asked about the Gachnang rumors, he told the Swiss press: "It would be very positive for Swiss motor sport, but for the moment, the new teams … no one has seen anything concrete (from them) yet.
"We will see who will really be there at the beginning of next season," Buemi added.