I'm sure at least one constituency would have nominated him - let's not forget that he's always been a prominent media personality and without London to distract him he'd be on HIGNFY almost constantly. It might be a more marginal constituency, both because the Boris brand has been tarnished with defeat and because people in such a constituency could expect Boris' common touch to swing more voters in their favour. If he unseats a Labourite or a prominent LD in 2015, that would bring even more pressure to bear on Cameron to bring him into a major Cabinet role.