Yup. IMO Midnight Sons is the direction they're almost certainly heading. A nice and clean divide in terms of threats faced and portions of the world (and/or universe and/or dimension) defended by said heroes.
Avengers (Earth): We know how this story goes. Earth's mightiest heroes yada yada yada. Loki attempts to invade, Ultron tries to exterminate, Thanos commits universal genocide and so on. (Agents Of SHIELD and Agent Carter probably fit under this umbrella as add-on goodies.)
Guardians (Cosmic): Marvel just blew the doors off its cosmic universe wide open. Guardians sequels... Adam flippin' Warlock et al, Nova Corps spin-offs and everything else is on the table.
Defenders (Street): Netflix actually seems the perfect place to explore the dynamics of superhero/vigilante culture in a street level setting. Bring on Daredevil, Jessica Jones, Cage and Rand for Wave 1. For Wave 2 go with Moon Knight and Punisher series, while continuing Daredevil for a second season while consolidating Luke Cage, Iron Fist and Jessica Jones into Heroes For Hire.
Midnight Sons (Supernatural): From everything we've heard, Marvel Studios is looking to Dr. Strange to begin their explorations into the supernatural side of the universe. Ghost Rider and Blade
cannot be far behind. If Marvel is concerned the commercial prospects of those characters, a Blade/Ghost Rider team-up might serve better. Then, a Midnight Sons movie along the lines of Avengers with Dr. Strange, Moon Knight (making the jump from Netflix to the silver screen), Blade, Ghost Rider and maybe other characters like Werewolf By Night, etc. The latter could be previously introduced in the Dr. Strange sequel.
And, of course, the Inhumans, who could possibly bridge the gap between the Earth based stories and cosmic stories while leveraging an Inhumanity-like event to flood the world with supers. Yes, yes... no one said "mutant".
'Tis a good time to be a Marvel fan. Long live the MCU.