peterv and ziocan,
thanks for the link (nice coincidence its arriving just in time this thread!)
So in the world of category SR4 rumors, this new onehttp://www.sonyalpharumors.com/sr4-sony-a99-has-100-25-600-iso-extended-to-50-and-102500/
supersedes and in part contradicts this one from October 4, 2011:http://www.sonyalpharumors.com/sr4-sony-ff-with-36-megapixel-sensor-coming-early-2012-nikon-d800-with-same-sensor/
The main differences being that instead of using the same 36MP sensor as the D800 in a new model in early 2012, that sensor will not be available until 2013 due to an exclusivity agreement with Nikon, and instead there will be first be a model with a new 24MP sensor. If so, Sony seems to be moving towards offering a choice of higher resolution vs higher speed, akin to the established pattern at Canon and Nikon. Maybe the SLT approach avoids Sony's previous disadvantage of not having the same level of high speed mirror flipping technology as Canon and Nikon, so a high frame rates model is easier.
My experience with this cluster of rumor sites (sonyalpharumors, 43rumors, mirrorlessrumors) is that "category 4" is more likely true than not, but far from certain, so I will stay tuned. [Edit: apparently until September, unfortunately.] Until I see more facts, I will stay skeptical (not cynical!) about "how new" a sensor of the same size and pixel pitch and using the same core sensor technology is, given the way that marketing talk has so often overhyping what turn out to be relatively minor updates.