With home prices rising rapidly in a key government survey, Fannie Mae and Freddie Mac could see their loan limits increase significantly next year – a development that may take a measurable bite out of the jumbo MBS market. Definitive data won’t be available until late November, but the conforming loan limit could be bumped up to well over $400,000 in 2006. The loan limit for the government-sponsored enterprises is adjusted annually based on…