Isaac is a hero from the Golden Sun series. He appeared as an assist trophy in Super Smash Bros Brawl and was rumored to possibly appear in Super Smash Bros. He did NOT make the cut. This implies the post from Sakurai stating "2 out of 3" on the subject of if Megaman, Isaac and Geno would appear in the game as FALSE.
Also if he gets in Smash, Goldsmith can finally rest in peace. He died 3 years ago and he won't stop haunting me by singing 7 Years by Lukas Graham.