Yep, the speed of REDCINE is the top interest for fast turnaround shoots like alot of SD work(which is still the majority) is. And as mentioned some producers will want the footage ASAP.
I know for sure that I will be asked to produce RED footage at SD. I am hoping REDCINE will be fast enough to convert to SD at least say at 2x(but 5x would be great) that way I'll be able to shoot 4k all the time to future proof any work instead of shooting in an SD mode. I also will consider doing all offline's at SD (at first) so as not to overwork and overfill my edit system.
But I admit that a SD recording mode would be nice to have up my sleeve!