The game wasn't that bad, to be honest, I liked it. Sure, it's not the Splinter Cell we have come to know and love, but it's not the end of the world, and it was defiantly fun. I still play it, so it has enough appeal to keep me interested.
Anyways, SC6, which should come out next year, is probably going to be what AC2 was to AC1. A complete revamp of the features, improving things, adding things, and taking out things that people didn't like.