I wouldn't think it's entirely planned ahead and I would have said the same as you, till I noticed a few little things.sanquin said:Same with bleach (Kubo planned to end it after Aizen, but his contract didn't allow for it), where it's very clear that he didn't think of the current plot in advance.
When Shinji first introduces himself he writes his name backwards and say's it's his talent. A good number of chapters later we find this was alluding to his shikai
Rukia telling Ichigo he looks like someone she knew (Kaien Shiba) in the first few chapters, it took till the end of the Aizen arc to reveal that was alluding to his dad's past as a shinigami and only in the current arc to confirm his relation to the shiba clan
I had also read that Kubo wasn't forced to do more arcs than he wanted but originally planned for there to be several more arcs (One for Kenpachi and Unohana, One for Ichigo's dad and another Ichigo arc I believe), but is having to tie everything together in the current arc due to bleach's reduced popularity.