The Hubble has the advantage of being above the Earth's atmosphere, but it has one severe limitation. It's mirror is only 2.4 meters. Scientists at the National Aeronautics and Space Administration want the next orbiting telescope to be much larger, thus allowing it to study objects that are too dim to be seen by the Hubble. A 6-meter telescope is seen as the minimum size to do the job, but that would be too large to fit aboard any U.S. rocket. There is talk about hiring the Russians to launch it with their more powerful Proton rocket.
Some scientists think a multiple mirror concept is the way to go.
The mirrors could be stacked for launching, and then assembled remotely into a single mirror. But that would require some very complex engineering. And there is one other limitation that may prove more formidable than the engineering.