I think there is a huge difference between being a monopoly and a duopoly. The fact that Lyfy can exist, and it is (at least currently) easy for both drivers and passengers to switch, makes it so uber cannot institute monopoly pricing. The best example of a network that can would probably be Ebay. Uber is definitely no Ebay, and I doubt it ever will be.
It is not going to be a duopoly forever. The current duopoloy is sustained by massive VC funding. In time the network effects and other advantages of size will lead to one winner taking all (in theory).
