The IRS web site I referenced in that post has been changed in the last day. Whether this reflects an actual change in plan, or just a big misunderstanding I can't say. Now their site has this header which is quite different from what was there last week:
State and county migration statistics will continue to be produced and posted on this site. Statistics for 1990 through 2010 are currently available. Statistics for 2011 will be posted as soon as they are completed. In addition, work is underway at IRS and the Bureau of the Census to develop additional migration statistics that take advantage of improved data that have recently become available.
So now the meta story becomes interesting. Was the migration data ever really going away? The reverb on that is still continuing. Historically the data came out early in the fall, but has been coming later in recent years.
The ironic thing in the end is that the original punditry all came from those who think interstate migration is impacted by differences in marginal tax rates between states. If that was true it would clearly show up most among the wealthiest and most mobile households. There is little evidence that is true from any causal standpoint.