Richard F. Syron, chairman and CEO of mortgage-securities giant Freddie Mac, says he remains “bearish” on the housing market and sees a rising tide of mortgage defaults and foreclosures on the horizon. He doesn’t believe a rebound will happen until late summer of 2007 when the nation’s housing inventory, bloated from weak sales, gets whittled down. “I don’t think it will be catastrophic and I don’t want to be the guy out there saying the sky is falling,” said Syron, who talked with Knowledge at Wharton before delivering a Wharton leadership lecture. “But I don’t think it will be a soft landing,” he said of the mortgage industry’s exposure to the housing slump.    Many people these days are facing higher mortgage bills because of adjustable-rate mortgages. At the same time, the labor market has faltered, pulled down by slower economic growth. Both the residential housing and the U.S. vehicle-manufacturing industries, which directly employ almost two million workers, are stumbling.…