Don't know yet but the showrunners are ready for season 5 to be the series finale if they won't be renewed.
http://tvline.com/2018/02/27/agents-of-shield-season-5-finale-series-finale-cancelled-or-renewed/
As the creative minds behind
Marvel's Agents of S.H.I.E.L.D. get ready to fine-tune the Season 5 finale, steps are being taken to see that it also satisfies as a
seriesfinale, should the ABC drama not get renewed.
“We are in process [of writing the finale],” co-showrunner Jed Whedon told TVLine on Saturday at the show’s Episode 100 celebration. Added co-showrunner Maurisa Tancharoen: “We know what it is.”
And what it
is, Tancharoen said, could serve as “either” a season or series finale.
Whedon elaborated, “Yeah, we’re ready for if this is the end. We’re definitely going to make it rewarding either way.”