There’s no question that Fannie Mae and Freddie Mac have become big time investors in the non-agency MBS market. What’s less certain, however, is whether the government-sponsored enterprises are going to remain at that level and what could happen in the market if they don’t. According to preliminary data gathered by Inside MBS & ABS, 29.0 percent of the $766.7 billion in non-agency MBS issuance produced through November was carved into tranches backed by conforming-balance…