2. A Failed Terrigen Bomb Will Give The Inhumans Their Powers
In case you're unfamiliar with the Inhumans comic lore, it features a substance known as "Terrigen Mist," one which effectively gives the titular heroes their powers. This fan theory attempts to explain why, exactly, an Inhumans film has been placed at the end of phase three for seemingly no good reason. Wouldn't it make more sense to end phase three with the results of the Infinity War, after all? Maybe... unless a Terrigen Bomb was somehow detonated during the events of the war in an attempt to kill Thanos. And what if said bomb failed, and the resulting Terrigen Mist ended up coming into contact with the yet to be confirmed characters of Marvel's Inhumans movie - superheroes who are literally created as a consequence of the Terrigen Bomb's failings. It's not a full proof idea, and there's are some details to be worked out (who decides to launch a Terrigen Bomb, for example?), but it's definitely a theory with some weight which would allow Infinity War a relatively smooth segway into the Inhumans film.