As you say Logan, all speculation. If however all these non-performing assets do go into a bad bank in the same way as Ireland did with NAMA, they will quickly find their true market value and quickly be disposed of at that. In Irelands case that meant a 50%+ fall in prices in less than two years.
With Spain, who knows? Some would argue that falls will be greater than that, particularly on the Costas, due to the size of the bubble, euro uncertainty, poor build quality, etc. Others would say less, given that Spain is more attractive to overseas investors, better climate, lifestyle, etc. Both arguments have their merits.
At present the only thing we can say with a reasonable amount of certainty is that prices still have some way to fall.