Ratings are the real infinite war
After months of speculation, and a tense week of watching ABC cancel or renew almost everything else on its roster, the network announced today that Marvels Agents of SHIELD will be back next year. There is no date set for Season 6 as yet, but a shortened season of 13 episodes, rather than the usual 22, would indicate that it'll be a mid season hold over.
This would make perfect sense, as its final episodes (most likely its VERY final episodes) would occur around the time that Avengers: Infinity War Part 2 (whatever the title may be) is in cinemas. Given that this is the end of Phase 3 (and many of the favourites of the previous years) it would also be a good time for the show to bow out. Season 6 will likely deal with the repercussion of the first Infinity War, leading up to its resolution. A perfect ending for the series.
The show isn't a massive hit for ABC, despite it being linked to the film franchise that has 6 of the highest grossing films of all time. Averaging about 2 million viewers on first air, it does however jump fairly substanstially in both Live+3 and Live+7, which can more than double its viewership. While this doesn't help ABC directly, it would seem to be enough of a win for Disney, who are obviously funding its continuation.
The same cannot be said for it's spin off, or sideways, show Inhumans. Despite premiering its first two episodes on IMAX screens, the quality of the show was... lacking, and viewers quickly turned off. It was officially announced last week that what everyone already knew to be true, it would not be getting a second season.
Marvel has many shows across multiple networks these days, with Netflix roster of Defenders (Daredevil, Jessica Jones, Luke Cage, Iron Fist, and yes The Punisher) all having (or will have) more than one season, The Gifted on FOX renewed for next year, Runaways on Hulu renewed for a second season, and Cloak & Dagger starting this summer on Freeform.