I'm just going to keep typing away about this because I find it interesting.
I think Kanan's chances are better than Shulk's. My support:
Famitsu gave The Last Story 38/40 (two perfect 10s), while Xenoblade Chronicles only got 36/40 (all 9s). This is the only review system I've found with a quick google to rate both games on an even playing field, and granted it's not that significant, but the fact that one received perfect scores and the other didn't is still something worth noting.
Xenoblade Chronicles has sold 230K copies, while The Last Story has only sold 180K. But that is on a global scale, which includes Xenoblade's recent release in Europe. If you only look at Japan sales, Xenoblade Chronicles only sold 150K. The Last Story is set for a 2012 release in Europe, and will undoubtedly make up and surprass the difference if it is similarly received in Europe.
Nintendo of America has leaked plans to eventually localize The Last Story. The same cannot be said of Xenoblade Chronicles.
Xenoblade being released earlier than The Last Story in Europe was actually more of a curse than a blessing. Sure, Shulk is more relevant now, but will he be in three to four years? If The Last Story is released in Europe next year and America shortly after, it'll be fresher in gamers' minds. Of course, this could go the other way as if either gets a sequel Xenoblade's will be sooner, and more likely to beat SSB4.
The development team for Xenoblade Chronicles was clearly second string. Takahashi and Shimomura are very talented (I'd even argue Shimomura could write circles around Uematsu)...but Sakaguchi and Uematsu are an unbeatable team. That and its art just kicks *** all around.
Kanan is a hot, scantily clad, sabre-wielding mage-chick protagonist. Shulk is a generic, spikey-haired, infinity-plus-one-sword-wielding fighter-dude protagonist. Scarcity creates value.