There's definitely some merit to this, but remember, the exact same thing happens with Video Cards, every 9-12 months the new GPU cards hit the market and are more efficient at mining. Of course video cards are much less expensive than the current round of ASIC's and can be resold.
Not *that* much more expensive. A 7990 will run you real close to what a 74GH/s bASIC will.
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Show me a single person who bought a 7990 for mining purposes.