It was reported yesterday that Hubble's primary (ACS) camera has failed, leaving the space telescope only partly operational until a workaround can be found. A real fix will await the 2008 shuttle servicing mission, which may extend HST's working lifetime to around the expected 2013 launch of the James Webb Space Telescope (JWST), formerly called the NGST (next generation space telescope). The picture shows a full-size JWST model on display at the recent AAS meeting in Seattle.
JWST is quite cool, and it will make use of some really advanced optics, materials, and other technology. One interesting application is the use of an array of micrometer scale "shutters" directly in front of the detector array of ESA's Near Infrared Spectrograph (NIRSpec), allowing scientists to selectively block out bright objects in the field of view to improve the instrument's sensitivity for fainter objects. Technology Review has a nice article on this MEMS-based technology here.
I'm hoping someone will build an add-on model of the JWST for Orbiter one of these days. There are some interesting orbital mechanics related to its planned orbit at the L2 Lagrange point that I'd like to try out (of course I could use any spacecraft in Orbiter to play with the orbit). In the meantime, if you'd like your own 3D model, you can download the parts and instructions for a paper model.