Yes, if it has blocked previous updates then it will continue to block the update.
No matter what update they are offering.
It is the
current firmware which tries to download a firmware update, and fails.
The method could break ONLY if you manually sideload a new firmware.
That new firmware *could* have code to detect this trick and disable it (and in fact, I believe it does)... but until you
open the lock, the newer and meaner firmware cannot start running on your Kindle.
tl;dr
The update blocker works when running on specific firmware, not when blocking against specific firmware.