A part 3 would be interesting. I mean if One Piece can continue for 10 years, I'm sure Naruto can too.
There will of course will be those who won't like part 3, nothing you can do about that. Every long running manga has highs and lows, that's just the way it is. But anyway, even though Kishimoto isn't a perfect writer (which some apparently expect him to be) he's still a pretty damn good writer so I'm not writing off a part 3 as bad yet.
And yeah guys, there'll always be whiners on the internet. I mean it's okay to voice your opinion, but the internet makes some people lose all decency.