No official sources, but a small bit of detective work.
I hate rumors, but it has already started on Twitter.
What a day! View 4 and vSphere update 1 tomorrow!— Barry Coombs (@VirtualisedReal) November 18, 2009
The talk is that View 4.0 will only work with ESX(i) 4 Update 1. View will be released tomorrow.
From the View Press Release
Pricing and Availability
VMware View 4 will be generally available on November 19, 2009 through VMware sales and the company’s extensive network of OEM partners and channel partners.
So officially it is November 19th, 2009 at least in my part of the globe - so get ready…
Put 2 + 2 together and what do you get? VMware View 4.0 and ESX 4 Update 1!
A whole lot of Virtualization happiness.