Ash and the rest of the anime is the reason Yellow Version was created and is why Pikachu is so popular and was included in the SSB series to begin with. I suspect that Jigglypuff got her fame in a similar fashion (although I believe Puff's male in the series).
Here's the article:
http://www.officialnintendomagazine...ii-u-and-3ds-sakurai-confirms-new-characters/
Upon re-reading it, though, it wasn't actually an announcement but more of a suggestion. However, going by what has already happened in the transition from Melee to Brawl (we lost Roy, Pichu, YL, and Mewtwo), I think it's fairly reasonable to suspect that veterans may be dropped if Sakurai wants to add new characters. I don't think any developers really want another DBZ Budokai: Tenkaichi 3.
This explanation makes sense, but at the same time, there are so many flaws with it. Why represent
gen III with
gen I starters when the game was already deep into gen IV? I think Smash Bros should have been fresh and introduced a new set of starters, since we'd already seen all three gen I starters in various forms multiple times in pokeballs/Saffron City in SSB 64 and SSBM.
As for the W/G/F starter trio, I was just confused as to why Sakurai chose those specific evolutions after there had already been so much obvious influence from the anime (Pika, Pichu, Mewtwo, Goldeen [she was never useless in the games or the manga, so her just flopping around in Smash is a clear reference to the anime], Puff, etc). Those evolutions were never prominent in the anime.
Then again, Sakurai's decisions have never been the easiest to understand.