This is once again one out of thousand of the same questions, however, since this is regarding an official installation of Android, that requires the boot loader to be unlocked, this might be a different case..
So let's keep it short: Does unlocking the boot loader and installing Android L voids warranty or not? And if not: How is it reversible so the unlock will be hidden?
p.s. Does this belong in the Dev section or here, since it's both a question and a developer thingy..?