One big question that was asked in the lead up to Avengers: Infinity War was whether the Marvel Cinematic Universe-wide story would incorporate Marvel's TV heroes such as the Defenders, Runaways, the Inhumans, or characters from Agents of S.H.I.E.L.D. But as it turns out, according to co-director Anthony Russo, there's a simple reason why Daredevil, Luke Cage and the rest weren't in Infinity War: there just wasn't room to tell their stories.
"We made the briefest consideration of it. When we’re alone in a room with [writers Christopher Markus and Stephen McFeely] we consider every idea," explained Russo on the Playback podcast. "But it seemed like the story that had been told within the movies was so specific and so elaborate already that we knew we already had our hands full with these characters. So it was the briefest of considerations."
That being the case, for 2019's Avengers 4 they might have the need for some reinforcements - and we have already made a list of the heroes on deck here.
It remains to be seen how or if Marvel's current TV shows will incorporate the events of Avengers: Infinity War into their plotlines.