MBS prepayment speeds are likely to climb higher because of falling mortgage interest rates, but industry analysts are undecided about how big a factor borrower burn-out will be. The Mortgage Bankers Association said its refinance loan application index climbed to 2575.9 in the week ending July 1, its highest level since early 2015. The index fell last week to 2295.8. The average interest rate on a 30-year, fixed-rate conventional conforming mortgage fell...