Well Kairi is more then likely getting trained by not one but two Keyblade Masters, granted one of them is retired. Personally, I love the fact that Kairi wields a keyblade now. Towards the end instead of the standard Donald and Goofy, it'll open up for Sora with Kairi/Riku as the back up. As a Princess of Heart, she'll be immune to any temptations Xehanort throws her way I think?