"OrionCA"
it's *unlikely* that
Hubble will remain operational until its replacement is launched but
not impossible.

The Webb Telescope will be a powerful sun of a gun, and will operate in the
infra-red band rather than visual, which is good because there is a lot of
dust in the Universe and we want to see what is behind it.

The thing that concerns me is that the Webb Telescope cannot be serviced
after launch. I rate its risk of failure as high, based on experience with
Hubble.