My guess is when the door opens for Directv subscribers there will be an app update. But I do what you do; I have downloaded Watch ESPN, Watch ABC, Watch ABC Family, and Watch Disney in anticipation of finally being able to log on and watch.
Edit: Maybe there will not be an app update before Directv subscribers are allowed to log in. I don't recall an update but Directv subscribers are now able to log into Fox Sports Go. Nice job DTV!