Not sure why Spondoolies announced the SP50 publicly, since they won't be selling it to the public. Kinda rude, actually, to tease us this way with UNAVAILABLE hardware.
Now, if they decided to sell a more affordable model based on the same chip, THAT would be worth announcing to the public.
The BIG thing I look at this miner and wonder seriously about though is the cooling. Even if we assume that those 6x 120mm fans are the HIGHEST flow Deltas at around 250cfm, that's not a lot of airflow to keep 16 KILOWATTS WORTH OF HEAT GENERATION cool. That's ballpark 50K BTU, which is enough to heat most houses in any climate short of Siberia or Northern Canada / Northern Alaska (do note that most houses have a lot more furnace than they actually NEED).
Good heatsink design can help a lot, but these units appear to have a similar problem to the SP20 - long boards, back part of the board getting already-warmed air flowing over it causing issues removing the heat. Those heatsinks they show better have a copper base plate, they're too short for a heatpipe design to help much if at all.
When the likes of TSMC step down their fabs to 20 nm or 16 nm
TSMC has had 16nm for a while now, just very low yields as they work to improve the process. fab companies don't run "just one size", they commonly have multiple processes available at the same time, just running on different machines in different partsof their multiple fab facilities.
I too would like to see Spondoolies make a smaller miner - single or 2 blade unit in a 2U shouldn't be hard at all for them to engineer, perhaps a 1U unit with a single blade at 10TH or so - though it looks like the blades might be too wide to fit in a standard rack-mount case horizontally. Perhaps a custom case?
A significant part of the equation is figuring out the likelihood of one of the producers dropping 2-4x more efficient gear in the middle of the aforementioned "storm".
I'd call that "when will", not "the likelihood of".
KnC I'm not worried about, even if their Solar has actually hit production I doubt it's going to make any big splash soon between yield issues and previous issues KnC has had with making RELIABLE chips (ref the MANY Titans with "dead die" issues).
21 so far doesn't appear to be targeting serious mining at all, VERY iffy if they're going to become a serious factor.
Bitfury, I'm guessing mid-to-late 2016 based on what they've already announced, will be hard to verify unless one of their "big corporate customers" speaks up (MBP perhaps?).
Bitmain or Innosilicon, I'd guess late 2016 at the earliest and more likely mid-2017.
Still at least one major unknown out there. What is Avalon doing?