Is there a program more commonly used in day-to-day Linux computing than SSH? I doubt it. Not only is it rock-solid, secure and versatile, but it also is extremely simple to use and feature-rich.

Disabling the ssh-rsa type of key will be a big issue though for those using smartcards to authenticate. A big usecase of OpenPGP cards is authenticating over SSH, and not being able to do this ...