On what grounds would they sue? Not only is it completely legal to copy a competitor's design (in most cases), Uber isn't selling this to other companies.
I don’t understand why the above user is getting downvoted to oblivion by people who don’t understand legalities. Trade dress[1] is a form of intellectual property. This is what prevents a company from copying a competitor down to the pixel. Apple and Samsung fought an infamous and long legal battle over this. [2]