Don't forget the controller and fan power, which could easily be another 25W (becoming 28 more at the wall).
The S5 is inefficient for the chip, because it's running at the top of what's possible for it. The S[odd] miners always did that, and the S[even] miners came later with higher chip density and lower per-unit power. Inefficient or not, the S5 was the most efficient machine available at the time, and nobody's really beaten it in a cost-effective way in the last 8 months. Sucks to say, but that was a pretty optimal design when you consider $/GH and that efficiency was already "good enough".
I'm betting they announced the chip as a preemptive strike on Spondoolies or LK Group announcing new gear (speculative, of course). Quite possibly they're only toying with factory samples now, which is why they aren't announcing an S7 design or any performance curves beyond the one data point. Or they're only letting slip a little bit of info and they've actually had them for months and just aren't telling everyone about their already-deployed S7 stacks because they don't want to yet.
That's true, it is still a good unit and will still be for a while. However the S1 was easy to undervolt. And quiet.(Still ROI able to me at 1J/GH) +Wifi
The S3 downclock well and is quiet. +Wifi (but no proper external connector iirc)
The S5 was meant to be super underclockable as well (remember the 0.2J/GH portion of their first information out?), but then suddenly it seem like it had to be rushed and sold cheap. As if they just wanted to kill off the competition. Only the latest PCB seem to handle undervolting. But i guess i'm speculating quite a bit in what could have beens.
And Yep, releasing those right this moment is still a waste for them. But the right time may come to be soon. They are possibly just keeping it as ammo to kill off the competition as soon as they come out.