Quouted from the Times Newspaper :-
"we won't come back (to silverstone)," Ecclestone said. "I am sure they (donington) will be ready but, if not, we will sign with another country. There won't be a British Grand Prix. Pure and simple"
So If Donington don't manage to rebuild / re-infrastructure within two years Bernie gets it out of the UK (as he's been trying for years), stuffs two fingers up at the BRDC and gets to say "It's not my fault" while counting his money.
I'd be very interested in seeing the contract / get-out clauses Bernie has with Donington