These predictions aren’t being pulled out of thin air. Piggingtonians are using the available data to make predictions — number of ARM resets, income levels, current interest rate and what have you. Is anyone going to be able to predict the exact bottom? Probably not many, but it looks like a good bet that the market is going to be lower next year than it is this year.
All one can really do is use the data to make estimates based on probabilities. If you think the time to buy is now and that prices will soon shoot up again then go for it. You can come back in laugh in all our faces next year after your house has doubled in value.