I think they are working to position skype of a selling point for WP7. It will be integrated into peoples hub. You will be able to switch to skype just like Facetime on iPhone. Skype will replace the cell tower when you are connected to wifi, etc.
But I would still release just a simple app for the sake of keeping current WP7 users happy. It is been way too long, so by now the app or update must be an asolute killer.