Be advised that Spyderco has announced this as a "rolling change" which means that current stock will have to be sold off before the 4s come into play. We went thru this before, if you'll recall, when the Chinook IIs came out. People were ordering Chinooks under the assumption a II would ship only to receive a first gen "old stock" knife instead. Be careful out there.
The only source I've seen so far has been Sawyer's cutlery on Ebay. He really is sending the 4s out. Folks have already gotten them in the mail. Check out the reviews and pics over at the Spyderco.com forum. Delicas only at this time. Enduras don't seem to be shipping just yet.