Despite BFL claims their product does not have many uses outside of mining bitcoins so the resale is almost nothing. I expect to get most of my profit when I sell the used hardware. A 6990 will be useful for years and years down the road.
As far as I know, we still don't know what chip this is. FPGA's are reprogrammable and have many uses
Those uses would be to students who would get educational discounts on brand new FPGAs and to businesses who are unlikely to buy from another person and probably not used either. I work for a large corporation and nothing could be purchased from someone off the street. It would have to be an approved vendor which takes quite the approval process. Even then the company I work for would never buy something used. So to address your answer, no there is still no resale value.