Several tips indicated that no Nikon pro body will be released before the summer. August/September is the time frame mentioned by several sources. Previous reports suggested that certain Nikon offices have already blocked employees from taking vacation in the last two weeks of August 2011. The CliQ show (formerly known as PMA) will start on September 6th, 2011.
This dpreview poster claims that the D800 will have a sensor carriage that can be removed by an authorized dealer. The rest of the specs: 16.4MP FX and 12MP B&W sensors, 3.3" LCD screen with a built in collapsible hood, new MB-D10i battery grip, 1/16000sec, full HD video at 120fps. This rumor could be influenced by the recent interchangeable sensor patents filed by Nikon. From patent application 2010-258657 :
"To provide an imaging device that has no restrictions on designing, can make an accurate alignment of a light-receiving surface of an imaging element, and has a removable imaging unit."
The German photographer Claudius Schulze reported on his blog that he was able to pre-order a Nikon D800 camera:
"Before teaching workshops this weekend in Munich and before flying to Yemen on Monday, I met with representatives of my suppliers, partners, and sponsors today. At that occasion, I was also able to (pre-)order the upcoming Nikon D800."
After exchanging several emails with Claudius, I learned that he pre-ordered the D800 through a Nikon rep from a local dealer. Some of the mentioned specs are: around 20MP sensor, full HD video and 100% viewfinder. Availability again is set for late summer.
Parts for Nikon D800 started to show up online again, like this LCD screen for example.