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?

Their experts probably agree. Statistically, the odds of invalid patents is very small but not 100% proven.

Trial, which if it had occurred is now a week or so away (no USPTO determination yet occurring, IMO sometime before the end of January but maybe not) was something neither plaintiff nor defense wanted to endure caused settlement with contingencies.

It is possible that neither side wished to wait on USPTO and neither side was 100% sure of the decision and analysis of the examiner. I think they have studied the examiners and have analysis of their track record just like TPL had of Judge Ward.

The Markman Hearing, from all that I read on this board, was a seminal event for TPL.  Yet, to state with 100% certainty that the examiner will find exactly as Judge Ward found is not a foregone conclusion.

Thanks for discussing this on the board.