This is extremely far from my area of expertise so I am probably wrong, but I imagine that at some point we will advance earth based telescopes to the point where we get diminishing returns when considering atmospheric disturbance.

At that point, it will make more and more sense to launch space based telescopes. But... if we wait until we reach that point in the diminishing returns curve, than we lost valuable innovation time/expertise in space based technology.

My hunch is that if we wanted to get the best telescope tech in any given period of time, we should do both and watch as the two types of technologies converge.