This is likely not gonna happen. Yea, its Goku, but its Goku. He's an anime/manga character first, regardless of how many video games he has appeared in. Outside of ROB, all of the Smash Bros. fighters originated from video games. Plus, I'm sure Akira, Funimation, Toei, Bandai Namco, and Bird Studio/Shueisha would want something close to a pretty penny to officially license him to get into Smash, considering how worldwide the Dragon Ball brand is.