To poke a hole in my original comment, presuming that the vehicles are still being driven by humans, there should be a hard floor in how low the price can go. If Uber is already at the a point in some markets where the drivers earnings can't even make up for vehicle depreciation & gasoline, that floor may have already been reached. At that point competitors may have both the same or higher price point and be slower than Uber.
Once driverless vehicles are brought in to the market, presumably these dynamics change again.
A third variable is the device which retrieves a vehicle. Google & Apple, the platforms where presumably almost all Uber vehicles are called from (not sure how many people are using the SMS feature or if it is still functional), are both working on producing vehicles. The current assumption is at least Google's will be self driving from day 1 and both may operate in a manner more like Uber than a traditional automobile business model.
There is a lot more certainty around how transportation will look, in general terms, by 2025 than who will be collecting the profits from it.