I think the only answer is to diversify as best you can, build a reputation of customers who love you to get word of mouth, and save as much as you can.

For an interesting view of where this has happened before, look no further than FB subsuming publishers via Instant Articles and Google recently doing the same with Amp. They stole all the control of the audience data from publishers, and give out whatever cut they feel is appropriate from ad revenue. Publishers refused to adapt or couldn't adapt fast enough and are royally screwed as a result.