RUMOR – Brawl delay had to do with a third party
This can be some what of a spoiler so it goes after the jump.
Those who have been following the development of Brawl extensively know that Masahiro Sakurai, the man himself regarding Smash Bros development, had a survey in Japan a few years back where he asked gamers what characters they would most like to see in Brawl. Every character in the top 10 of that list is in the game except Geno, who was the #1 character on the list.
Apparently Square-Enix pulled out of the deal with Nintendo to put Geno in the game. Brawl then had to be delayed so they could take Geno out of the game.