The rumor mill is ramping up again about the much anticipated Canon 5D Mark IV thanks to a post by Northlight. According to Northlight, the EOS 5D Mark IV is going to be announced until fall 2015 at the earliest. Furthermore the 5D Mark IV won't be announced until the 5DS and 5DR are shipping in "reasonable numbers".
According to various websites the sources inside Canon have mentioned that sales of the 5D Mark III are still very good. I suspect 5D Mark III sales were boosted once the 5DS/5DR were announced because many photographers, myself included realized the 5DS/5DR is not a good camera system for general use. I personally had been holding off on buying a new full frame camera waiting for something new from Canon, but finally bit the bullet and just bought a 5D Mark III.
The sources are also say the 5D Mark IV may not come until after the announcement of the 1DX Mark II.
Rumored specs for the 5D Mark IV:
28 megapixel sensor:
9fps
4K video
Improved external flash control