I am not really good at this stuff, but I see separating focus. Call it UberAuto, Uber would become UberAuto's parent company. UberAuto could receive new VC rounds and a new CEO appointed, focus on the autonomous development, while the parent company focuses on its core business and get ready for IPO.
Waymo is a spinoff from Google (and Alphabet is Google's parent company). Ebay, HP all have its own spinoffs.
Edit:
In fact the new Uber CEO Khosrowshahi guided Expedia spinoff. See [3]. So a spinoff isn't unlikely. The spin-off could be just a research entity, but license to parent company later.
In business, spinoff typically refers to creating a new company with separate ownership. E.g., PayPal is a spinoff of Ebay and Agilent is a spinoff of HP but Waymo is not a spinoff from Google, because they share the same ownership.