I remember there being a number which initially went unsold, but then heard rumor someone bought them all out for less than MSRP. Rumor is rumor, can't found it, but some users did report being unable to purchase the remaining 900 the same day. Because of this, and wanting to project 'worst-case' scenario for planning purposes, I presume the full 2500 to be sold.
I think that was just a face-saving maneuver by KNC, to close batch 1 and price reduce the remaining machines and call them batch 2 so they could get rid of the unsold stuff. I think KNC is probably regretting building the Titan as much as its customers are regretting pre-ordering the Titan.
On the mining side of things, they are getting killed by languishing BTC prices.