No, it won't.
> The fundamental economics don't change...
They don't change for Uber, but they do for drivers.
> It will take longer to get to penetration levels that result in sufficiently high utilization.
You seem to be under the belief that supply drives demand here. That's not the case.
The economics of utilizing a taxi service can be markedly different for suburban consumers than urban consumers. Point B is frequently more distant from Point A in suburbia, so the average cost of a taxi ride tends to be higher. Thus the relative attractiveness of paying for a taxi ride decreases.