We could hope, but it's probably just pikachu. My bet is any clone characters are alternate skins;
Pikachu > Pichu
Lucario > Mewtwo (Given the moveset is similar)
Mario > Luigi**
Peach > Daisy (duh, but possibly better than melee)
Sonic > Shadow > Silver > Possibly all 'mid-sized' sonic characters?
'though it's questionable if the alt skin would show up as the different icon(leak picture), or not. If so, Lucas > Ness
**This isn't necesarily true or untrue; however, there's a possibility of Luigi as an alt-skin, using the poltergeist2000 rather than fludd, and the 'rocket' rather than the cape... Even so, Luigi's a clone character nontheless in most instances, anyway.