I really like the simplicity of the old animation system. Mecanim is great and everything but its made for complex animations. When making a simple game the extra power seems to get in the way. Do you ever think the developers will remove the old animation system?
The Only reason Legacy animation system still exists is to provide backward compatibility with old projects.
Unity dosent suggest to use legacy animation system for new projects however.
So i am assuming it might be removed somewhere in the future.