I think we have learned to be quite conservative to avoid disappointment - but remember that before the EB1 12K bombshell dropped, we expected spillover to be quite low last year as well. So all we know, we might get another 30K-35K spillover.
Demand density post 07/07 is the wild card. Based on PERM data, we are considering the period from 07/07 to end of 2008 as being quite dense - but there are a lot of moving factors there - including demand destruction due to lack of EAD, lower dependent ratios, duplication of PERM filings (in general, Indians who came to the country later have tended to have more two-income households with both spouses on independent H1Bs and independent I-140s; just my impression).
With 07/07 inventory gone, we are quite blind now. A few months will clear the air. Hopefully. In any case, I remain optimistic about future movement. We have crossed the densest year (2007), we have a potentially-equally-dense-but-probably-less-dense 2008 ahead of us followed by a very weak 2009. Unfortunately, 2010 is again quite dense - but that is not of immediate concern.
PS> Look at how the Chinese EB2 demand has fallen from a cliff around 2007. I won't be surprised of EB21 follows the same pattern with some delay.
PPS> If you have not watched yet, please see the recent South Park episodes about Mexican immigrants going back - its funny because its true (almost).