They would lose the contract for sure, not sure about getting sued. Besides, there is one more thing, the 6 months time limit is starting from when an acceptable final RC that meets the contract criteria is delivered to VUG. They could keep rejecting RCs for minor issues and delay the 6 month...
It might have worked in the past cause a lot of people have gotten tours of Valve. Right now they might be just too busy.
You might have a much better chance once it goes gold, then again, they might all go on a long holiday once it does.