frobinso.. Not sure, but I don't think it's possible to infringe an invalid unenforceable patent. You lose on validity and enforceability and you automatically lose on infringement. Win on infringement, then you win on validity. mo.
How would it be for them to come back with an infringement finding, but that the patent is found to be invalid and/or unenforceable - in that case we would be in the same boat, or find a bigger hole in it.