I believe this has also been mentioned in the Echo but the council will have to be very careful as they have legal obligations to spend money on things which are for the benefit of their ratepayers and also they have certain budgetary obligations.
They could argue that, arranged properly, the stadium could become a facility which would benefit Southampton ratepayers. However, it may depend on whether the art collection is part of an arts budget or capital. Also, the wheels of government work very slowly and it may take many weeks to get funds agreed etc.