I think the US will see stagnation from late 2011 and eventually noticeable decline beyond 2013, however it wouldn't describe it as collapse. I also expect China to get back to +10% growth by 2011 and continue to hold this until then. I more or less expect the US government to mismanage their economy under increasing pressure in the following years, the bloat of government and debt ensure this. There are other scenarios I find plausible that have a similar result. Regardless I would put about 30% probability for 2018 being the year, I would also put 25% on 2022 and 20% on 2027 if I was a betting men.