I'd bet on Google, Tesla, and Mercedes before Uber, since they all have vehicles with more than a week on the road and cash-positive revenue streams to support further development. Uber burned through ~30% of their $11B in cash just in 2016 alone.
Uber will be able to get cash in the future if self driving tech matures to transition. It'll be a multi billion dollar opportunity, capital will be lining up to invest in the ride hailing market leader.
I'm very doubtful. The financial market conditions that lead to the unicorns are drying up, and like most unicorns, their early/current investors have some extreme shareholder's agreements which make the companies very unattractive to new investors.
