How exactly can they play hardball when they don't 'own' anything but their subs? While novel, there's nothing all that unique or profound about the platform itself.
Subs aren't that hard to gain (or lose) in large quantities. Especially millenials are quick to dump for the new trend. Amazon, hulu, and plenty of others are ready, willing, and eager (and trying) to take over the space themselves.
Unless I'm mistaken, netflix is in AWS so amazon obviously has the capacity to server up everything that netflix does (and more) ... given licensing to do so. So if netflix told the big movie studios to go suck it, i'm sure amazon would happily use that to negotiate something.
Even audio streaming is struggling because of licensing costs an order of magnitude higher than broadcast radio.