"When we do release new firmware, we ensure the new YubiKey will function the same as older versions, so there is no need to purchase new YubiKeys to ensure compatibility."

Seems false, doesn't it?

Ugh that's really frustrating. If it's for security, why can't they just blank the key like they do when the master key is used?

Ahh, I should have made that more clear in my comment. Definitely frustrating, as those dang keys aren’t cheap!