If the autonomous stuff works (HUGE if) it would completely change the core business. I can't see why they'd spin it off. Why sell your future unless you think it won't work out.
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.
[1]: https://www.nytimes.com/2016/12/13/technology/google-parent-...
[2]: https://dealbook.nytimes.com/2014/10/15/companies-seeing-the...
[3]: https://qz.com/1063313/new-uber-ceo-expedias-dara-khosrowsha...