The Juno New Frontiers mission to Jupiter has been officially approved: http://www.jpl.nasa.gov/news/news.cfm?release=2008-222
I'm a big fan of this mission. It will be one of those quiet missions -- not a lot of public pizazz -- that will greatly deepen our understanding of gas giants. This mission will probe Jupiter's interior in multiple ways to determine key ratios of elements, the magnetosphere, and the deep structure. It will also study the upper atmosphere and auroras. There will be wide-angle photos of at least the poles. (I'm hoping they can take pictures of the cloud deck near perijove. Since the orbit carries the craft near the terminator, the clouds near sunset should be spectacular -- if such shots from a spinning craft flying past the planet are technically possible as anything but a smear!). No meaningful photos of moons. Just solid science on a key type of planet.
You can read more at the mission's website: http://juno.wisc.edu/