The issue now is that the Middle class stand to lose their houses by the end of the year because over over leveraged and over borrowing. Now that's why it's getting so much (more) attention.
Maybe a small percent will find it advantageous to walk because they're underwater and can fanangle and can financial magic to buy a different house cheaper.
A small percentage might not be able to pay their 2021 payment because of gas prices or job loss.
The biggest risk to prices or banks is likely collateralized commercial investors.