That's yet to be seenNothing's stopping you from playing purely stealth.
To be fair, even the older SC games weren't pure stealth, there were spots late in that you have to fight your way through enemies who know where you are. Those parts generally sucked.
Now that I look at the card that came with my copy of AC2 I realize it says nothing about a demo. It says "Free exclusive Splinter Cell Conviction Download" That probably means it's an exclusive bit of media or a shitty screensaver. It's definitely not a demo because according to the instructions you download it from their site.
So it seems confirmed that as a Splinter Cell game, this entry will completely and utterly fail.
Another victim of casualization
Yeah, the problem is that they didn't add options. In this game you HAVE to kill the enemies to get past them, there's not even a knock out option. The developers basically removed stealth and replaced it with action : /