Hi! Here's a quote from an interview with Jay Cocks(The writer of Gangs of New York):

"Cocks: No, it was about 182 and at the end it read, "Part One." Part Two was going to be about the building of the Brooklyn Bridge. But dreams die hard, and I'm gonna get to do that for HBO, but not with the same characters"

Now you might say that a project without Martin Scorsese(We are not aware if he will direct this, or will have any involvement at this time) would not be successful. While Martin Scorsese is a great director and writer(Casino and Goodfellas) he was not responsible for much of Gangs of New York outside the direction. As far as I read he choreographed the fight scenes and added religious symbolism, but the actual script was completely done by Jay Cocks. I state this because many enjoyed this movie because of the excellent script. I have high hopes for the project. We will get a chance to see a continuation, except with different characters.

Those pesky directors; always takin up all the credit for directing a multi million dollar production.
In short: What the fuck are you smokin!!!?

Look what I am basically saying is the sequel has a chance to be great even without Scorsese. Martin Scorsese does not take all the credit himself, but critics give him all the credit. The reason why the sequel might fail is the cast. They should hire some talented actors.

Il silencio è d'oro e la parola è d'argento.

It could work. I mean sure the film centered around a select few out of the masses, but they could do the same for the sequel. It could still be old NY, still be the gangs but from a different perspective.