Most banks are still sitting on an inventory of foreclosed homes that are not yet on the market.
I don't think you'll ever see all of the foreclosed on the market at once for one simple reason: The economic law of supply and demand would apply. It's already a buyer's market - this means there are more homes on the market than there are ready, willing and able buyers. If the banks were to openly market all of the foreclosed properties at once, they would flood the market with homes for sale and thereby force home values even lower.
By holding bank on the inventory of homes, the banks are helping to slow or stop the free-fall in home values. As the market turns around and it becomes a sellers market, you may see more of the foreclosed homes come on the market - but at a controlled pace.