I personally believe there may be a slowdown but much faster than expected the private market will pick up the slack. People will still desire to own homes. There will be a huge market for those who are willing to take a "risk" and loan to people while keeping the loans in house. Many small local banks already do this. They may require a certain amount down but that is only reasonable especially when we have seen so recently how it doesnt work with looser criteria. Just as a down market opens up many investment opportunities for us investors so could a down banking/loan market create many opportunities for small up and coming banks and investment firms. Lastly I think interest rates are bound to rise and when a home loan with 20% down gets a bank 10% or more interest they will be jumping at the opportunity to get in the business again.
Even if I am wrong I believe it is in the long term best interests of our country to not have a quasi- government entity controlling real estate in such a direct way.