Key takeaways:

• The CFPB's new Qualified Mortgage rule is expected to define the core of the U.S. mortgage market of the future. 
• The final rule provides a conclusive safe harbor for Qualified Mortgages in the prime market, but only a rebuttable presumption of compliance for higher-priced loans. 
• A new 43% debt-to-income ratio requirement was added by the final rule, with a temporary exception for certain loans that meet GSE and government agency underwriting standards. 
• The rule will become effective on January 10, 2014.