Well, I might make note of something that makes a difference - they say 1Th/s, not 1.5.

Additionally, that 1 Th/s is with multiple chips in a box, and the number is unspecified. My understanding of full-custom ASIC processes is that chips are cheap to make, once the NRE is recovered. Like, REALLY cheap.
So I do believe it is possible, but I also am of the opinion that they are staking an awful lot on the outcome.