I really don't think that duplicating libraries (a requirement for OSX-like .App bundles with no external dependencies) or apps checking and self-updating by app-specific methods is a good solution either.

For every duplicated library, you introduce the security and stability problems of that specific version, each will have to be addressed by the application provider, who may or may not be interested in the latest developments in the libraries it uses, instead of the original software developer. This thing can grow nasty in no time.