PTSC/TPL has "gone back" and will continue to.  The INTENT of each settlement to date, I can assure you, was to gain compensation for possible PAST infringement and possible future infringement.  For all intents and purposes, except public perception, the word "possible" in that statement can be replaced with "actual" (assuming the patents are valid). But they (licensees) are unlikely to freely admit infringement/wrongdoing, so settlement language isn't likely to include an "admission".

It only just occurs to me that THIS may be why TPL has stated their intent to simply go for settlements in one-time payments (instead of going for a lump sum to cover past infringement, and ongoing royalties for future infringement).  I suspect it would be much easier (considering public perceptions) to obtain the one time payment, and thus be permitted to say it is for "POSSIBLE past and future infringement" and opposed to a payment for the "POSSIBLE" past infringement and royalties for future ACTUAL infringement.  It would be an admission (unless they suddenly came out with a whole new chip product line concurrently - vitually impossible). 

Just thinking out loud, which is very dangerous when you KNOW nuttin'!

Welcome aboard POBS!  Hope this helps.....

SGE