We had a GTK+ meeting during the Guadec BoF days. It was a long and good discussion touching on many issues. Notes from the session can be found here. Hard to summarize, but some highlights:

• There’s a lot of interest in adding a flow box / grid companion to our new list box widget, and also adding a model-view separation. Expect to see work on this next cycle
• We’re starting to make progress on clutter integration. Things are happening, but may not be ready for the next cycle
• 3.10 will have pretty complete hi-DPI support. Just waiting on cairo, now.