Services trimming their libraries will certainly become more commonplace as they seek to cut costs and drive up profits. This will remove a giant reason to subscribe to them in the first place.
Compound this with ever more streaming services, and it is an easy bet people will turn back to piracy. In this case, I think it is an ease of access issue vs a cost issue. Having 3-4 streaming subs is still vastly cheaper than cable, but when shows start vanishing and libraries become smaller and smaller or filled with junk, people will look to alternatives.
These days, VPN's are cheap and it has never been easier or better to set up a media streaming app in your own home. I've seen one that automatically downloads shows and movies with no input from the user. That is the type of ease of use coupled with the notion that content will always be available is likely to be a draw for a lot of people.