It has been the statement of the Wizards people that all 5E material will be backward compatible with the new revision. Feats are an optional rule. I like them but if they are no longer optional and being rewritten and if level requirements that didn't exist before come into being, then that's not backward compatible. If it becomes optional to add a feat to a background I have no issue with that if legacy versions are allowed. i.e. if the new version omits an ability that you want to use, you still have the option to use the old way.