It probably won't ever be serviced or upgraded, for several reasons:
It's orbiting at the Earth-Sun L2 Lagrange point, with a perigee of 374,000 km
While we can put astronauts in space, we don't currently have any orbital vehicles with on-orbit satellite maintenance capabilities, since none of them have airlocks
The latter could very well change over the next few decades though, and the former may become economical, so I guess it can't be entirely ruled out.
But the landscape of the space industry is changing very rapidly. With a fleet of hundreds of reusable rockets floating around, the accessibility of the Hubble may change.
Of course, at that point it might be better to just send up a bigger instrument.
It's orbiting at the Earth-Sun L2 Lagrange point, with a perigee of 374,000 km
While we can put astronauts in space, we don't currently have any orbital vehicles with on-orbit satellite maintenance capabilities, since none of them have airlocks
The latter could very well change over the next few decades though, and the former may become economical, so I guess it can't be entirely ruled out.