Way to use an extreme example...
Well it was your example. Mining isn't that big. GPU market in long run will absorb sell off just fine.
The discrete GPU market is $20B a year (note that excludes integrated and hybrid GPU/CPU products).
Lets say all 10TH/s are GPUs (not a single CPU miner, no FPGA, no botnets, etc).
Lets use an average of $0.50 per MH.
That's ~$5M in GPUs used for mining. Hell lets double that and say ~$10M in GPUs are used in mining world wide.
That is out of a market that moves $20B in product annually.
Now lets pretend they were all purchased in one year.
Under the most unrealistic of scenarios GPU used for mining are still <1% of global market.