Before gen 6 hit I thought he'd probably be replaced by whatever the "new Lucario/Mewtwo" was. But there wasn't, really--there was Mega Lucario. Even if Zoroark had been popular, its gimmick wouldn't really translate to Smash well. I think now that Lucario is exactly they really wanted and didn't have when they put Mewtwo in Melee. Mewtwo was iconic and has the toughness to balance out Pikachu, but I wonder if they wished they had the heroic mascot of justice and honor thing that Lucario has going on.
I'd rather neither have the roster overcrowded with Pokémon nor have the playable pokémon be overcrowded by veterans, so I kinda hope Jigglypuff gets some retirement... though I guess if Mario has five now, so could Pokémon, including two extras via a Pokémon Trainer. I wouldn't be disappointable at all if Calem or Serena made it in with the same sort of starter setup Red had in Brawl. Froakie line is my favorite of starters.