Even if you did swap a symlink to upgrade to GLES3, all the apps will still call the GLES2 functions. No matter what, the devs would have to go back and rewrite their app to actually use the new features.
Many apps detect GL level and adapt renderers accordingly.
Still, it's not just graphics drivers: there's the oft-cited security patches, but also features for user-facing interfaces; Ie, an update to a URL parsing library might add additional codepage support transparently to an app that uses it.
