The Hubble space telescope probably has done more science, & we gained more knowledge from it than anything else or anybody we have ever sent to space. It's sad that we can launch probe to Pluto & other planets, but we can't build a spacecraft to carry a repair mission beyond the very low orbit of the space station to maintain this very excellent & important scientific device.
But that may change someday. There is now at least a slight possibility of there being another maintenance mission to Hubble.
According to a report, the servicing would provide an insurance policy in case the James Webb Space Telescope, fails or malfunctions.
Sierra Nevada, a private spaceflight company, has worked for years on a miniature space shuttle called the Dream Chaser, based on older designs generated in the early days of NASA. The craft is only cleared for automated flights and may resupply the ISS as soon as 2019. The Hubble mission would require a human-piloted variant relying on infrastructure that already exists in the ship's design.
The possibility is currently in the (very) preliminary stages. It would represent a public-private venture that would drive down federal government costs by teaming up with private spaceflight companies, a model that is expected to be utilized in the administration in general.
Along with the Webb telescope, NASA has two telescopes based on modified versions of the Hubble design donated by the National Reconnaissance Office. One such mission, the Wide Field Infrared Survey Telescope, will be utilized as an exoplanet and dark matter hunter to be launched in the mid-2020s. Plans for the other telescope have not yet been announced.