I don't know the specifics on the deal between Netflix and Marvel as far as series cancellation goes, but I know Netflix wanted to lower the episode count on the seasons and Disney/Marvel held them to the original contract of 13ep seasons.
We all know how much most of the series could've used 3 less episodes each. Would've also brought down the cost of each season, or allowed more for each episode... lower ep count didn't really help The Defenders tho :/.
Either way, I've heard there's a 2 year hold after cancellation, where Marvel may or may not be able to use those specific characters, but not in their own solo shows.
The loophole around this might be that they can team them all back up in The Defenders (subtitle "S2") as that was never renewed for a 2nd season, and will be over 2 years old come Aug 2019.
And that could segue into maybe the Heroes for Hire series that everyone has been asking for.