Actually, it only demonstrate it's possible for them to be leaked. This is a rather obvious conclusion.
However, if the signing keys remain valid forever and signed binaries don't have to be re-signed when keys expire, you have essentially an infinite amount of time to leak (or crack) the signing keys and the likelihood of a leak will approach 1.
I am much more concerned by the increase in computing power than with leaks. The value of a valid signing key in a UEFI secure-boot world is high enough to ensure someone somewhere will spend inordinate amounts of money and/or computing resources to obtain a valid key. How much does leaking a key cost?
However, if the signing keys remain valid forever and signed binaries don't have to be re-signed when keys expire, you have essentially an infinite amount of time to leak (or crack) the signing keys and the likelihood of a leak will approach 1.
I am much more concerned by the increase in computing power than with leaks. The value of a valid signing key in a UEFI secure-boot world is high enough to ensure someone somewhere will spend inordinate amounts of money and/or computing resources to obtain a valid key. How much does leaking a key cost?