User blog comment:DancePowderer/What's the Deal with Cactus?/@comment-4493594-20130326183906/@comment-94.68.165.51-20130326234727

"If he is dead then his sole purpose of existence was to die for  the sake of Luffy's character development."

Couldn't say it better, but unlike you I feel this is a crap reason of existence. Sabo didn't affect Luffy's character development on a way to make his existence mandatory for the series. So, I have to that that:

If he is dead then his sole purpose of existence was to amuse Oda by creating an interesting character with no real use. A character he used to pass his time and make One Piece a little longer.

No, I don't think Oda sketches that way, and that's the only reason I believe that the Sabo case is not closed yet.