Last time, it dragged on a couple days past their original expectations. The early notices said don’t contact tech support before 9/27. I saw in the trouble shooting forum the date of October 1st.
(“Please do not contact Cleverbridge or Pixologic Support prior to that as they will not be able to assist with such inquiries until October 1,” in http://www.zbrushcentral.com/showthread.php?160733-ZBrush-4R2-Troubleshooting-FAQ&p=891426&viewfull=1#post891426 .)
I’m more concerned now that people are getting duplicate OSX licenses instead of windows licenses, which suggests their list is SNAFU (again) as evidenced by lack of coordination between “R2 is coming!” emails and license emails.
As someone who bought from Pix directly in the 1.55b days (ah. the sweet days before super-duper-anti-piracy-prevent-you-from-running-the-software-you-paid-for), and before DumbBridge, I have to request my stuff manually half the time, or re-initialize my licenses if I change the graphics card, upgrade the PC, or even (gasp!) attach a raid to the SATA port.
They could at least do us the favor of letting us know what percentage is sent out so we would have some remote idea of when we might see the actual product, but that would ruin the suspense. After all, everyone wants software distribution feel like winning the lottery, right? I usually figure on a month from when Pix starts these rollouts so I can be pleasantly surprised if I get something usable in less than week. 
(As always, my tongue is firmly planted in my cheek! :lol:)
-K