I was out shooting a couple a few day ago both with the a850 and a77. Shooting a dropping sun. The EVF was tricky to use. I certainly couldn't depend on it to make sure exposure was right. In the end the OVF was a much better option.
With that said do you think you could drop a traditional OVF and go to a EVF? Me I could do it but it would make taking pictures harder in tricky lighting. In the end you still have to know what you are doing to nail a shot. The EVF isn't the next coming to digital photography and I think hard nose pros are not going to easily except it.
The VF on the a850 is huge and you could think you could walk out into the scene looking through it. It is easily the best VF I have ever looked through.
So my questions are. Do you think the next full frame Sony will have an EVF? Do you think it will be easily excepted by pros?
Me, when I am hitting the road the a850 is my go to camera. As basic as it is it is still a lot easier camera to deal with than the a77. The a77 is really not that much smaller than the a850 and adding an EVF to it isn't really going to make it that much smaller. Also considering there is no way you can use a EVF without a grip. The added EVF and live view eats batteries and the a850 last a long time just on one battery.
So are you ready to ditch that OVF? Not me, not now. I love my a77 but the a850 more.