I played Splinter Cells 1 - Chaos Theory, and I completed them with the leave-no-trace mentality, including the self-imposed kill no-one mandate. I would wait patiently in the darkness memorizing patrol patterns and using my sticky cameras to knock out guys by hitting them on the crown of the head, or grabbing a guy without alarming the man standing next to him and dragging my victim into the shadows. I was a super-spy. And I loved it.
But...
it would be foolish to believe that this is a bad evolution for this series. In story terms, Sam is breaking from the well supported super-spy that he was to the rogue knife in the dark that he is now. The mentality of the main character has changed from calm and collected to pissed off and vengeful, therefore the gameplay should reflect that.
Secondly, who is to say you can't continue patiently waiting for the moment to strike? The stealth aspect has changed from slow and taxing to fast and dangerous. From the videos I've seen, this is still very much a Splinter Cell game, but at the same time it isn't more of the same. Pandora Tomorrow was more of the same. I really liked it, but they didn't start innovating the series beyond what it was until Chaos Theory.
This, in my opinion, looks like what Assassin's Creed should have been.