BBC put out an article on the topic. They make it seem that ESA
should probably pick one "Large" class mission (Laplace, Tandem,
XEUS, Spica) and one "Medium" class mission (Cross-Scale, Marco
Polo, Dune, Space, and Plato) by 2017 and 2018, respectively.
Obviously these missions are well down the pipeline and a number
of things need to fall into place for these birds to get off the
ground. Also, the "Large" missions are budgeted in the range of
EUR650million, which is not enough to get a meaningful mission
to the outer planets. Thus, there needs to be some international
collaboration. Whether NASA and ESA can pull off another
Cassini-Huygens class success story remains to be seen, and as
far as I can tell the international community hasn't decided
whether Jupiter or Saturn is a higher priority. Hopefully this
problem stimulates some constructive
dialog.http://news.bbc.co.uk/2/hi/science/nature/7053057.stm