As far as the lifetime warranty question goes, I don't think that question has been answered yet. However, with most of Walther America's competitors in the US market offering lifetime warranties, I would be highly surprised if they didn't.
Pages 32/33 of the owner instruction manual answers the question.
1-year warranty to the original owner, which is what Walther has done all along ... with the exception of a limited lifetime warranty originally offered for American owners of the PPQ (which they started when it was being imported by S&W's Walther America).
The limited lifetime warranty appears to be carried over to the PPQ M2 being imported by Walther Arms, as can be seen in their instruction manual on their website - http://www.waltherarms.com/resources...ries%20USA.pdf
The P99 appears to continue with the same 1-year warranty, as is stated in the instruction manual - http://www.waltherarms.com/resources...nual%20P99.pdf
I'd guess the PPX is intended to offer the American commercial (Non-LE/Gov) market an affordable sporting/defense pistol of standard size, much like S&W did with the SD series after they released their M&P (and which eventually became the SD VE, with the Sigma disappearing from their catalog).
The change in the mag catch button on a couple of the new models would seem to make good sense, as it's described as a traditional design. Walther's been using it for decades, and the American customer has often looked askance on other designs. Seems like good business sense based upon marketing research.
Not sure if or when Walther will develop an armorer program in the US for their new import company (although they certainly have one in the rest of the world, and they worked with S&W to maintain one for P99/SW99 during their alliance). If they do, and it becomes a field class, with one held close enough to me to be reasonable, I might attend another one. (I did 3 of them when S&W was giving them.) They've been continually making revisions, refinements and subtle design changes in their 99 series over the years.