I think DOS is frustrated with USCIS that they haven't kept a count on new I-140s approved with older PDs to see what is the upgrade demand.
I think DOS is in game mode now ..it will do what it did with family-based cases. It will push dates as far as it can to use up all visas and then retrogress in October.
PS: In the downturn of 2008-2009, a few Indians abandoned their GC process and went back to India. Most attorneys advised them to withdraw their applications. I thought we could possible see a miniscule effect in the USCIS inventory. But that was not to be.
I am sure we will see a drop of a few thousand applications when compared to our estimates on PERM approvals.