The biggest energy improvements are going to come post release, as developers start making app nap sensitive changes.
If you look at the wwdc sessions or read the ADC articles, there are several things that can be done to ensure lower energy use and more app nap time, but they take work; it's not all for free. Also, once the energy use/abuse numbers start being thrown around, devs are going to get pressure from users/enthusiasts to make these changes.
While bundled and system apps should be more energy sensitive at release (as Apple is ahead of everyone on App Napping things), its going to take some time for 3rd parties to follow suit.