On Betfair you can still place bets on Biden being next president
Chart of Betfair market from Betdata.io – 7.50pm BST
The Betfair definition of this market is “Who will be elected to be the next President of the United States of America as a result of the 2020 presidential election?”
All we have had is media organisations calling it for Biden and it could be a few days before the counting is finalised. So I suppose there is a theoretical possibility that Biden won’t do it. However the odds of about 1/25 for what appears to be a certainty seems very generous.