I really hope then end the series on a solid note. There are series that keep going and going and the villain never dies (Inuyasha comes to mind).
Bleach has had strong character development and a great overall story. There are certain plotlines that were fairly pointless; the bount story arc comes to mind. There have been too many repeated scenes/flashbacks. But, overall, they're heading off against Aizen, who has been the "big bad" since the story began; though it wasn't revealed 'til after Ichigo saved Rukia from execution.