As you know, miners have paid enormous prices for ASICs (>$10K for Avalon, BFL doubled prices but still receiving many orders) in hope to make easy money. I think most of them probably not realized how FAST difficulty will go up! When this will happen, ASIC miners will see that they have no chance to even recoup initial investments with current BTC price (~$100) and won't sell mined coins in the loss waiting for a better price. If I am right, this could lead to Bitcoin supply drop and price hitting new heights, may be $500-$1000 at the end of this year.
The idea is sound, but I think the miners' behaviour will depend very much on market sentiment... which we're not having a great time predicting at the moment.
My gut feeling is that mining supply is a very small part of the recent downward price movement. If you're significantly invested in the Bitcoin ecosystem, why dump coins for cheaper than people are demonstrably willing to pay for them? I think the dumps are more speculative... or manipulative.