
But coming up on the horizon is the James Webb Space Telescope;

Isn't that a groovy picture? All colorful and ebby'ting...
Here is a comparison of the sizes of the two 'mirrors':

Note that while the main mirror of the Hubble is a single piece of reflective material, the JWST has a combination of segmented mirrors joined together to produce the final result.
"The telescope has an expected mass about half of Hubble Space Telescope's, but its primary mirror (a 6.5 meter diameter gold-coated beryllium reflector) will have a collecting area about five times as large (25 m2 vs. 4.5 m2)."
more to follow...