The Saints had planned to sell of part of the site to supermarket giant Asda in order to finance a 4,000 boost to their capacity to 17,500.
They currently have to play Heineken Cup games at the home of football side Milton Keynes Dons as Franklin's Gardens does not meet the required standard.
But Northampton Borough Council argue that the planned superstore would suck the lifeblood out of trade in the town centre and are expected to turn down the proposal.
Chairman Keith Barwell told The Daily Telegraph on Thursday: "This could be our last season here because undoubtedly, while we are waiting for the council, we are already having discussions with the banks and have a plan B."