The lastest in a series of astronomical Decadal Surveys was published yesterday (8/13/10). Like previous astronomy surveys, this one ranked space- and ground-based missions in priority order. Unlike previous surveys, this one (like the concurrent planetary Decadal Survey) placed considerable emphasis on analyzing the technical maturity and probable cost of the missions it recommended. Advances in astronomical research over the last decade has created a new set of priorities of future missions.
I will have my own analysis in a few days after I wind up some travel. In the meantime, the journal Nature has a good overview of the reasoning behind the priorities and list of the recommended missions, facilities, and research programs. You can also download the complete report.