The UK may not be the only country to raise the price of the Nikon D4 and D800 cameras. There is a good chance that this will happen also in at least one more European country (maybe Norway?). For now this is just a rumor, but I was told that Nikon D4 orders has been put on hold awaiting the new prices. I have no information about a potential price hike in the US.
If you are in the UK, maybe it's worth checking DigitalRev who currently have the D4 in stock for £4,689.00 (free shipping to the UK).
Update: several readers confirmed that pre-order UK prices will not be changed/increased. Nikon UK also confirmed the price increase on Facebook: