i'm more inclined to think wsj plays a big part in the continuation..
hope gintama won't suffer this fate. sorachi looks like he has a backbone, at least.
I doubt it. If end on a high note, it's a welcome (but don't overstay). Plus, I can see both studio and Sorachi making fun of themselves to try to earn more money by continuing. Like how they make fun of themselves of why they're making fillers, though it's very true for the reason.
Am I wrong in saying that Naruto is the only big thing SP has?
No. They had Tokyo Ghoul but they ruined it and DVD sales were low thanks to sabotage of Root A. Seriously, the final volume was lowered than the previous ones. Why? Because they kittened it up.