SHIELD will have to time travel throughout its own history. This premise for Agents of SHIELD's final season is one that is definitely familiar to superhero fans since that's essentially what Legends of Tomorrow is all about.
Legends of Tomorrow was the second Arrowverse spinoff that began in 2015 (Legends of Tomorrow has become the best show in the Arrowverse. However, even within that shared universe, the Legends remain outlier weirdos.
Turning Agents of SHIELD into Marvel's version of Legends of Tomorrow makes sense. Agents of SHIELD season 5 already dove headlong into Marvel timeline to stop the Chronicoms.
Ironically, Agents of SHIELD and Legends of Tomorrow already had a great deal in common. Both series are spinoffs but they are also essentially the bastard stepchildren who are not necessarily part of the mainline events of their respective superhero universes. Neither was invited to the big crossover events of the past year; the Agent Carter) and that will probably remain the case when the series wraps next summer.
Since Agents of SHIELD is going head-on into Legends of Tomorrow's time travel territory, hopefully this will let Marvel's series embrace their own inherent weirdness. After all, Agents of SHIELD has only one season left and, at this point, they should be freed up so that anything goes. This isn't to say that SHIELD should have their own giant blue furry Beebo, Bollywood musical numbers, or that they should save Barack Obama from a homicidal talking gorilla like the Legends have, but Agents of SHIELD can certainly get weird. One of the best episodes of season 6 was "Fear and Loathing on the Planet Kitson" where Sarge-is-really-Coulson story that ended with a brand new Life Model Decoy of Phil Coulson ing the team.
Since Agents of S.H.I.E.L.D. season 7 has nothing left to lose, there's no better show for them to emulate than Legends of Tomorrow to give fans one last unforgettable run of episodes as a final farewell.
Marvel's Agents of S.H.I.E.L.D. season 7 arrives summer 2020 on ABC.