The Space Shuttle Atlantis launched earlier today to perform the fourth and last servicing mission of the Hubble Space Telescope. This Shuttle mission should restore the functionality of the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS). The shuttle astronauts should also install two additional instruments: the Cosmic Origins Spectrograph (COS) - a high-spectral resolution ultraviolet spectrometer - and the Wide Field Camera 3, an upgrade from WFPC2.
Hubble over the years has made a number of discoveries at Io including observing surface changes between Voyager and Galileo (such as a major eruption at Ra between 1994 and 1995) and sulfur gas in Pele's plume. These discoveries were made using the full-set of instruments onboard the space telescope, and no doubt these new instruments would certainly be useful for the study of Io, particularly studying the gases in Io's atmosphere using the COS spectrometer. Because of the high demand on telescope time, Hubble is not well suited for change detection, but certainly comparisons between any chance images of Io could be used for this purpose, but they would need to be large changes like the one at the Ra Patera eruption.
Link: Hubble Servicing Mission 4 [sm4.gsfc.nasa.gov]