At that point it is not clear which sensor will be deployed in the upcoming Pentax 645D medium format camera. My first guess few months ago was for the KAF-39000 from Kodak.
The only problem is that neither of those sensors will give us the reported "1.7 times bigger than a regular full frame sensor" ratio (official information from Pentax).
A regular full frame sensor is 36mm x 24mm, or 864 mm² with 43.3mm in diagonal.
The older medium format KAF-39000 sensor is 49mm x 36.8mm, or 1803mm² with 61.3mm in diagonal.
The new medium format KAF-40000 sensor is 45.76mm x 35.34mm, or 1617 mm² with 54.78mm in diagonal.