originally it was supposed to be Q3 2011,
True, but go back far enough and it was 2H 2011, so no real change overall.
As to the details for the Q1 2012 release, I read it in the following thread
http://forums.anandtech.com/showthread.php?t=2175389&highlight=2011
That being said, there are several other s2011 threads that are about a month old now, so might be a few more links in those ones.
SB-E pushed back to Q1 2012. But then after that intel started pushing harder for some to release this year, and so has been the cause of Intel lowering the specs of the inital motherboards from high end to the second lowest and by cutting the original 3 cpu types at release to just 2 (the more expencive 6 core ones).
Judging by all the "trimming" going on, It feels like any sort of Q4 2011 release will be a paper release only. We can live in hope though.
Though IB IIRC is down for a Q2 2012 release (April is the expected month at last check).
edit: I am sure I read somethere that March was mentioned, but the linked artical from the before mentioned link mentions January. But releasing at that time does appear a little silly given most hardware wholesalers (at least in my country) are basically shut for most of January.
edit: regarding IB, found this about it for March 2011, but I think someone mentioned April as a more realistice time to see the products in stores.
http://forums.anandtech.com/showthread.php?t=2173233