I think we have enough Legendary Pokémon already, and we really don't need any others.
I can't even think of any other Pokémon that deserve to be Legendaries.
Oh, and Dragonite, Tyranitar, Metagross and Salemance are the Ubers of each generation (though in Hoenn, many argue over whether the Salemance or Metagross line is the Uber evolutionary chain of this region), each having, I believe, base stats of 300 or something. No way do I think they should be Legendaries- they're powerful enough as is.
I can't see any other Pokémon as being Legendary, and heck, the wave of Hoenn Legendaries doubled the number of them (seing as there's a sum of 11 Legendaries from Kanto and Jhoto). If you count Mewtwo as a Legendary, as well as Lucario, and heck, if Manafi is also a Legendary, then I believe we have a whopping 23 Legendaries already. More than enough, if you ask me...
~Psychic