The first season of Inhumans has come to a close and leaves the Inhuman race in very different place than they began, and could have a direct impact on season five of Agents of S.H.I.E.L.D. After eight episodes of the Royal Family mostly in hiding on Earth, they successfully returned to Attilan... only to go right back to Earth. The season 1 finale of Inhumans leaves the ancient home of the enhanced race in ruins, leaving the entire population of Inhumans to now reside on Earth. The drastic change in setting will make a big difference in a potential second season of Inhumans, but also puts it in prime placement to have an impact on Agents of S.H.I.E.L.D.
Without the guarantee of a second season on Inhumans, the ending serves as a closing of one story, but the beginning of a brand new adventure. If that second season doesn't happen - and the show's current ratings aren't doing it any favors - the results of the Inhumans finale could be completely forgotten about and retconned from the canon of the Marvel Cinematic Universe. But, until that point comes (if it ever does), making Earth the new home to the entire Inhuman race is only going to raise more questions about a potential crossover once Agents of S.H.I.E.L.D. returns.
Earth is the original home to Inhumans after all and they've called Earth their home in various forms throughout their comic history. For the purposes of the MCU and with the information the finale has revealed, the Inhumans have made friends with Louise's (Ellen Woglom) employer Callisto Aerospace. The government agency has set up a new base of operations for the Inhumans in an unspecified location on Earth, but most likely on the islands of Hawaii. The levels of secrecy and non-descriptive nature of their exact whereabouts leave the door open for some wiggle room and loop holes, but it will also force viewers to overlook Coulson and his team - that includes a few Inhumans of their own - to not look into their arrival.
Agents of S.H.I.E.L.D. has never been perfect when it comes to exploring loose threads that dangle from the MCU's continually growing timeline, but it would stand to reason the arrival of the Inhumans would be something they'd want to look into. They can probably overlook a group of ninjas attacking New York and understandably stay out of anything involving the movies, but the ABC connection will make it that much more odd if Inhumans' finale doesn't leave some sort of impact on S.H.I.E.L.D.
The good news for S.H.I.E.L.D. is they have plenty of time to possibly figure out what their move is going to be. The season 4 finale sent the story for season 5 into space, which makes the timing of the Inhumans' arrival on Earth that much more ironic. Regardless, with Coulson and his team trying to find out where they are and how to get back home, the writers will have some time to course correct and accept Inhumans' ending - if that is what is desired.
If Inhumans' ending is addressed, it is even possible the effect will come into play before the team returns to Earth, as the collapse of Attilan and the mystery organization Coulson's crew is now involved with may want to look into this event too. The fifth season will see the team back on Earth at some point, and when they get back, finding out more about the Inhumans' arrival and their relationship with Callisto Aerospace is going to be something viewers of both shows will want addressed. S.H.I.E.L.D. could brush it off without much concern, but the Royal Family's presence on Earth could also pave the way for a big crossover. Whatever path is inevitably chosen, the Inhumans finale, at the very least, forces S.H.I.E.L.D. (and the larger MCU) to accept or avoid the latest Marvel production.
Agents of S.H.I.E.L.D. premieres with a two-hour episode on Friday, December 1st on ABC.