The same way Spoondoolies don't know yet. Except Friedcat is honest, and is telling you he doesn't know, and providing the best estimates he can.
Fair enough, but fact remains that BF and SP are aiming at 2-3x better power efficiency (and ~3 months earlier time to market). Whether they can pull it off, time will tell, but that goes for AM as well.
Let me get this straight, Bitfurys estimate of 0.2 w/gh is 2-3 times better than AM's estimate of 0.22 w/gh? And where did you hear Spondoolies was aiming for 0.1w/gh this year? (not that it matters as they miss more targets than AM)
I'd also love to know how you know that SPtech and Bitfury will have hardware 3 months earlier when taping out 1 month later than AM.