1) You don’t need in-camera pixel binning, do it yourself in PP.
2) I don’t see why A77 users should be concerned about compacts.
3) You’d have to ask 5DMkII users, from what I read it can introduce Dynamic Range issues.
other questions:
1) Doubt it. The crop is there for electronic image stabilisation. I don’t think they’ll provide a way of switching it off, but it would be nice.
2) Don’t hold your breath for tethering. It may never happen. I have to also use a Canon (long story) because the A77 doesn’t have it!
3) According to Sony, the 1600 ISO video limit is to prevent the sensor from overheating due to more power being drawn by the sensor at higher ISO. So I doubt it will be changed.