Thanks to Steven K1ST for alerting me to the fact that the Lab599's TX500 transceiver will soon be available for sale from Ham Radio Outlet.
Yes, one is on the way to my QTH!
HRO's page for the transceiver mentions that the rig has passed its FCC certification. The owner's manual is also available for download.
So far, I don't have any indication of when the rigs will begin to ship but when I receive mine, you'll be the 2nd one to know.