By the time robotics advances to that point, it would most certainly be economical to manufacture a significantly more capable replacement telescope, wouldn't it? As far as I know, there isn't any particularly exotic materials in Hubble, it's just a big heavy precision manufactured (lol) object.

Even right now, it seems like the real cost of a falcon heavy launch is relatively low. We would get more science for the money by mass producing several higher performance telescopes with fewer reliability requirements.