People have said the same about FB and Amazon. I agree that they wont be able to stay at loss for ever, however once the cheap cash runs out there's nothing stopping them from bumping up the rates a bit and/or growing less aggressively.

Yes, they will loose x% of users, but the ones that stay will be served at a profit. At this point, Uber is likely too big to fail.

Anecdotally, I have used Uber from the beginning and never even bothered to install anything else just because there was no compelling reason to, I don't see that be different for many users.