Phoenix real estate on sale

As highly publicized over the past 18-24 months, home prices in Phoenix metropolitan area have backed-up about six years in established neighborhoods.  The fundamental question is, "Where's the bottom?"  Might today's buyer reasonably expect another 20% decline (equivalent to an additional 2-4 year back-up)?  A new phenomena for me is the market splitting into two segments; wholesale (investors intending to "flip" properties and buying at auctions, short sales and foreclosures) and retail (end buyers intending to live in the home or rent out as a business).

Clearly the next crash will be in commercial properties.  Phoenix currently has more than 33 million square feet of empty commercial space with an additional 3.5M under construction.  Sale and lease asking prices have declined only slightly in the past 12 month, but in the past few weeks it seems as EVERYTHING has been posted for sale; established leased properties (including $150M in Penske automobile dealerships), vacant buildings and raw land....signs everywhere!  I wonder how much more TARP money will be needed to absorb these future bank losses?