Unless we get blessing of Dave Rossum, I would be very cautious to speak of "standardization", or even a "SoundFont3 standard". EMU is dead, unfortunately. And there is no such thing like a "SoundFont standardization committee".
I see it as follows: Musescore has established a "de-facto" SF3 "standard" to support compressed samples. That page in our wiki
is an attempt to write up a spec for this Musescore implementation, which aims to be extensible whenever possible. And that's how it's gonna go. There will be an extension to the extension for the extension. Such an extension may or may not be documented. I don't see that there will be an authoritative place for those extensions. And finally, it's up to the software projects to implement them or not to.
On the other hand, the more you craft into that specification in the first place, the more unlikely it becomes that it will be adopted by anyone.
Because of that, I currently don't see a necessity for a revisal or update of that wiki page.
And one last thought: I would be very cautious to keep bumping the major version of the SF format over and over again. E.g. FLAC compressed samples can already be stored in SF3, i.e. no need for SF4 as originally requested. Any extensions should be as backward compatible as possible.
Tom