Normally shield bonuses do not stack, this is understood. Has this changed at all with the advent of the Kasatha as a playable character race (IE can a Kasatha carry more than one shield and receive AC bonuses from each)?
No, any more than a human could carry two shields and have their AC bonuses stack.
They do get the benefit of being able to wield a +5 shield and a +1 shield with a bunch of useful properties without paying through the nose for high pluses, which is not inconsiderable. And they can wield a greatsword or polearm the entire time.