To make another note about the sub-plots revolving around legendaries, Game Freak has gotten fairly smart about obtaining some of them in BW2. The post-game episodic legendaries in BW2 were all very clever, save for hunting down the Regis (which is always a pain for no good reason). Most of them were cleverly set up to become a part of the post game once you, as a player, are glad that the bridges no longer have technical issues and the fatass convention in the gate north of the White Forest/Black City has packed itself up, and are eager to go look at everything the game kept away from you. Suddenly, Pokemon that were traditionally roamers are hitting up Unova one at a time, which would make a very exciting series of captures for kids who started with Gen V, and they each (with the exception of the regis, again for no good reason) come with some buildup, either through a legend that an NPC tells you about or actually bumping into it before it runs off, that makes you want to find them prior to battling them. I always thought the pixies had a correlation to the chinese natural elements of Fire(Victini), Water(Manaphy), Metal(Jirachi), Wood(Celebi), and Earth as the central element(Mew, as the origin from which other species of Pokemon evolved from). If/when they make the next pixie, I think it would either suprecede Mew as the embodiment of Earth, or they'd find some new way to tie them together thematically.