http://alpha-t.net/faq/

Its less than $3k final cost (incl VAT & delivery) and 100W consumption for 5mh. Even at a much higher price, the power requirements would make all the difference

If they hit the market in any significant quantity, pretty soon even the best GPUs won't be covering power costs.
Or rather they will be doing just that as I suspect much of the GPU load that is currently profitable will be withdrawn and only the most efficient will remain.
It will probably take a second generation to eliminate them completely, just like with bitcoin. The FPGAs of 2012 were much better than GPUs but they did not make them irrelevant. Current scrypt asics seem to be at that level of relative performance rather than the bitcoin proper asics of 2013

That is not to say I expect GPU mining to die.
Already as mentioned there are coins using modified scrypt incompatible with asics.

But I am curious what will happen with scrypt-coin prices