As to whether this happens the biggest single factor may be how baby boomer dealers respond as their book selling careers wind down.  There are thousands of them.  Dealers tend to hold prices until the final years and then sell en mass to other dealers for some combination of money down and a share in the proceeds over time.  But if there are fewer future dealers as appears likely, such deals on good terms may become difficult to obtain.  Dealers tend to shun selling at auction but should they change their view the pressure on prices could be extreme.

No doubt the best material will hold up and even prosper.  The middle market is less certain.  The key may be the ability of buyers and sellers to find each other more efficiently.  For myself selling "The American Experience" at Bonhams made 2010 an extraordinary year.  I learned a lot and lived through it.  I also now know that the ideal auction consignor of unreserved material is dead because to get through it you can't feel too much.

As to what this means to me as a collector I continue to acquire material.  I am both careful and aggressive.  The volume of complex, interesting and often unknown  material flowing into the rooms, appearing in dealer offers,  showing up on listing sites  and on eBay - is stunning.  The selection of material has never been better.  As to what such things are worth and whether they are appropriate for my collection of the Hudson River Valley I now gauge against their history and rarity, buy or make offers.  It's a different world and for book collectors who are prudent, the best possible.