...not one to normally feed into the general rumor mill, but just got a bit of information from a reasonably credible source (local reseller), his comments were apart from the name and obvious improvements around features (as seen in other recent EOS models such as live view and sensor cleaning) was that it was going to utilise the EOS 1DsMk2 16MP sensor as it is a proven sensor that provides a good upgrade and leverages existing technology investment.
Time frame according to him was around October/November.
Not sure of his sources though, he is not one to form unsubstantiated speculation though.