" we will pay you 100s of millions of dollars .....some of it (X) by a certain date  date and the rest of it (Y) when all re-exams are complete and in your favor" 

So, they accept the validity of the patents by agreeing to pay "x" now, then say that they might not be valid in the future? Why settle at all if they believe that the patents can somehow be invalidated in the future?

Be well