I think that Lea and Kairi will become Keyblade Master since strength doesn't matter, is all about strength OF YOUR OWN HEART!!! you need to have super balance between light and dark in your heart (that going to be tricky for Kairi since she pure light and lea will be easiler for him) is not about strength of the power, why do you think Xehanort went to take Terra body instead of Aqua well is easy
- Terra have stronger body than Aqua
- Terra don't know how to control the darkness within him and Xehanort use that as an advantage!