@Kingoffans:
I think the bigger question is, is it mainstream enough?
You mean One Piece, or Nicktoons Network? Because Nicktoons Network, as has been pointed out, is a digital cable channel, and therefore, isn't mainstream at all. It used to be where Nickelodeon aired all their old shows (their version of Boomerang, I guess), but now it's where crappy shows that were miserable failures on Nickelodeon or shows that will eventually go to Nickelodeon and BECOME miserable failures go to moulder out the remainder of their existences (I'm looking at you, Kappa Mikey.) As for One Piece, I think it's mainstream enough (and would fit in well enough with the Avatar demographic) for them to consider, but the fact that Nicktoons Network is a digital cable channel isn't going to make One Piece much more mainstream then it already is. It'd be nice for me at least, since I get Nicktoons Network… Still, first Nick gets a new X-Men show, then Nicktoons Network (maybe) gets One Piece, which may eventually move onto regular Nick (if Nick gets it in the first place). I see block possibilities with One Piece (if they get it, of course), Avatar (what's left of it and the sequel series) and the new X-Men show. A new Toonami...