I'm a Fedora user (personal desktops), a RHEL user (production machines at work) and a CentOS user (hobby servers that don't need paid support). I have no desire for extended support for Fedora. It makes no sense whatsoever. The support you get is a new release every 6-ish months... and that is an insane amount of work already.
I would not like to encourage Fedora users to hang on to older versions of Fedora even if there were enough volunteers to keep building security updates for legacy versions... because that would splinter the user community into more versions of Fedora... and no matter how well the volunteers updated things, legacy releases would always be a second class citizen. There are already too many users hanging on to older Fedora releases without updates... and Fedora would be better to continue improving the version-to-version upgrade process.
Fedora is all about trying to keep up with the pace. If you want the long support, get RHEL and/or CentOS... or do what I do... use the right desired one for the desired job.
I do disagree with the idea that Red Hat would have the desire/ability to kill this proposal or to ignore it to death. If the Fedora community really wants it, I think it will happen. I'm just in the camp that doesn't want it.