It just didn't really sell. I suppose long range wireless video cards are just a very niche product, and either there wasn't enough demand or the people who wanted it didn't happen to find this card. It did work amazingly well, having zero lag over an extreme range. Unlike basically all other wireless products ever, it actually went as far in actual use as it claimed on the box, too. To this day it amazes me that we have the tech to go 100ft with lagless 1080p video, yet it's near impossible to find a remotely gaming worthy wireless keyboard and mouse that can reliably go more than 9 feet.
Either way I wouldn't say WHDI's been abandoned, it's just only available in external devices since we're the only ones that ever thought to put it in a graphics card. It's certainly a far cry better than Intel's WiDi which is cheap but has more lag than the mars rover.