I think the point is to start shipping mediawiki with common extensions there.
This is great if we are going to version the extensions with the version of MediaWiki shipped, and backport changes to those extensions to ensure they get security and bug fixes like core does. Alternatively, we could provide a way for extensions to be easily upgraded to compatible versions, similar to wordpress and other sane applications.
If we don't plan on doing one of two things, then we are forcing our users into the crapshoot that is finding the correct extension version, or possibly running insecure or buggy extensions.
Respectfully,
Ryan Lane