After a rough start to its freshman season, Agents of S.H.I.E.L.D. began earning back fans with the fallout from Captain America: The Winter Soldier, which completely turned the premise of the show on its head. Then, in season 2, Agents of S.H.I.E.L.D. moved past simply reacting to the movie side of the Marvel Cinematic Universe by introducing Inhumans to the show - most notably by revealing Skye to be Daisy Johnson a.k.a. Quake (Chloe Bennet).
While viewers may have thought Agents of S.H.I.E.L.D. was setting up the MCU's planned Inhumans film, reports that the movie was going to be canceled, then news that it had been removed from the release schedule, seemed to indicate S.H.I.E.L.D. may be the only chance for fans to see the Inhumans in the MCU. Now, it seems Agents of S.H.I.E.L.D. may have more freedom with the characters than they did previously.
In a roundtable interview with the press, including io9, at Comic-Con International in San Diego, executive producers Jed Whedon and Maurissa Tancharoen spoke about how the delayed Inhumans movie affects their corner of the TV universe. Whedon said they have a bit more freedom to include classic Inhumans:
“We do have a little more freedom. We’ve told a couple of seasons of stories but now we do have some more freedom. So when we return to focusing on Inhumans, we’ll be able to do a little bit more.”
Of course, Agents of S.H.I.E.L.D. has been telling stories surrounding the Inhumans for close to two seasons now, since season 2 dealt with figuring out the Obelisk, discovering Terrigenesis, and learning about the Inhumans home of Afterlife; meanwhile, season 3 saw the formation of a the Secret Warriors while S.H.I.E.L.D. attempted to bring in as many newly-transformed Inhumans as possible - not to mention the season's main villain was the Inhuman Hive.
To that end, it seems what we know about season 4 indicates Agents of S.H.I.E.L.D. will be moving away from Inhumans story arcs. The season 3 finale introduced LMDs, or Life-Model Decoys (robots designed to take the form of a living person), and the show confirmed the addition of Ghost Rider Robbie Reyes (Gabriel Luna). Certainly, it seems likely these storylines are what Whedon refers to when he mentions the show returning to Inhumans, since LMDs and Ghost Rider don't fall under that umbrella.
Still, fans of the Marvel Comics who were disappointed to see the Inhumans movie removed from the release schedule will likely be excited by the prospect of classic characters such as Black Bolt, Medusa, and/or Crystal coming to life in Agents of S.H.I.E.L.D. However, that said, Marvel Studios head Kevin Feige has said the Inhumans movie is still expected to be part of the MCU at some point, so it's unclear which classic Inhumans Agents of S.H.I.E.L.D. is able to use.
Agents of S.H.I.E.L.D. season 4 premieres September 20th, 2016 in its new timeslot, 10:00pm EST on ABC.