The reason that mortgage interest rates have been hovering at historic lows in the last couple of months (in the low 5’s) is that the Federal Reserve has been feverishly buying up mortgage backed securities (MBS). A MBS is basically a bundle of mortgages that banks put together and sell as investments. Banks sell mortgages because that gives them more money to lend to others. The easier it is to sell these MBS’s the lower rates can go. So with Uncle Sam willing to gobble up the MBS’s for sale rates stay low.
According to this article, the Fed is committed to keep at it as long as it takes to help turn around the economy. That is a good thing if you need a refinance.