Just because RS5 does not offer MT, I don't even think about it, similar reason for C63.
I had a C63 for couple days, omg the sound was awesome (still can't forget), power/torque was exotic. But after 2 days I was bored of it. Gas/Break Auto is just simple boring.
RS5 will have great DSG, similar to DCT in M3.
I don't know, if it's going to be a sports car, I need that third pedal to control my car.