Hopefully we'll have cooler stuff in place by then. I'm assuming it can also be serviced, like Hubble.
Maybe technology will develop enough to allow us to send drones to work on JWST, but today this is still just a dream.
PS: I'm just a random code monkey on the internet, so take these comments with a grain of salt.
Let’s say we wanted a constellation of telescopes to do full sky surveys of small objects in our system for asteroid detection. Do those need to be kept at near absolute zero to be effective at that task?
Webb has a specific mission of imaging deeply redshifted space. I would hope in 20 years we’ll be able to launch bigger, simpler, and cheaper designs for more “pedestrian” missions.
https://space.stackexchange.com/a/38415
https://time.com/6127003/webb-space-telescope-discoveries/
> Webb faces other operational challenges, however. Hubble has been kept alive in part through maintenance and servicing runs done by astronauts. Webb’s great distance from Earth makes that kind of house call impossible. What’s more, in order to remain stable at its gravity-balanced Lagrange point, Webb needs a thruster system, and a thruster system requires fuel. The telescope will launch with a full tank, but that will be only enough to keep it operating for a minimum of five years and a maximum of 10. In theory, a refill ought to be possible, and the telescope is actually equipped with a docking target to accommodate an incoming spacecraft that could conduct a refueling and extend the JWST’s life. It’s an appealing idea, especially considering the telescope’s dizzying price tag. That spacecraft, however, does not yet exist, though it could within the next decade.
To be honest, sounds like a cool project to start working on, with the idea that it becomes an off the shelf capability for future space observatories. SpaceX's Dragon can carry a 6000 kg payload, and already supports autonomous docking with the ISS, for example.
https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-exces...