When all the wallets upgrade to using HD Wallets (BIP 32), then those backups will become interoperable between Bitcoin applications.
Concerns about Armory disappearing and not being able to access your keys are unfounded. Armory is thoroughly distributed around the world, and even if Armory Technologies magically disappeared, and took the git repo with it, and all the google download links, you'd still only need to find a single person who has an installer for any version of Armory ever made. Not to mention that someone could probably pretty easily write a backup reader to extract the private keys out of it. Not to mention that the above scenario is ridiculous
