The promise of a second grand international space venture is attractive, and promises tantalizing benefits as evidenced by the completion and manning of the ISS. However, there are several factors that present serious roadblocks.
First, the economies of all three agencies' nations are in a shambles, and attempting to raise the public funds to support an ONGOING project on the order of multiple billions of dollars and tens of years for each agency represents a substantial uphill battle. This is likely to be true, even WITH the current optimistic outlook in the economy, for at least several years to come.
Second, public support is fractured at best. There are: 1) those who deride the cancellation of the shuttle and decry the dependence on Russia for manned launches, 2) those who yearn for the Apollo-type nationalistic program, and 3) those who prefer a Mars-first approach. While these represent a strong base of engineering, science, and advocacy based support for the "Research Base", the general public, and its rising youth are more interested in "living, working, and migrating" to the lunar "SETTLEMENT". This is NOT the mission described and envisioned by governmental agencies. As such, gaining public support to fund such an effort that sends a handful of astronauts is likely to be a very hard sell.
Third, as we have seen with the ISS, Space Shuttle, and most Government sponsored space projects, they are plagued with massive cost-overruns, project delays, infighting, and a consistent EXCLUSION of public participation. In and of itself, the announcement will result in a flurry of news items, but as with Apollo after 11, the ISS, and the space shuttle, the lead time typical of government projects fosters a substantial loss of interest by the public, and as the years drag on, public support degrades, and like Apollo, the ISS and shuttle, funding will be eroded to such a degree that the project will be severely crippled.
A critical factor to this public support, the ISS has not generated any results (other than presence) that can be appreciated by the public. There have no great discoveries from the station, and no announcements of commercial benefit/breakthroughs or new products that the public would embrace. As such, there is a public undercurrent that makes the ISS appear to be just another government boondoggle with no public benefit.
Additionally, as these citizens continue to cry out for further social program spending, and the governments counter with increased austerity measures, the likelihood of any public funding for a grand space project that is geared ONLY to science is an uphill battle.
Space is a dangerous place, and instead of treating it like the harsh, deadly, life-sucking frontier that it is, our planners continue to believe they can "make it safe" for our Astronauts to travel through increased research, development and technology.
Frontiers have been conquered by settlers - not astronauts/scientists/explorers. In every frontier of the past, intrepid explorers opened the frontier (as NASA, RKA, ESA, JAXA, and CSA have done) proving it was possible, but then those governments opened the frontier to individuals and groups to pursue the settlement and commercialization of that frontier. It is time for government and science-explorers to step aside and foster the migration that will provide the support for public spending necessary to resume science exploration once the settlers get there to provide long-term support.