Shadow Complex setting very specific week-one sales records on XBLA, Epic and Chair would be kind of nuts to not consider a sequel. One job listing out of a recent crop on Microsoft's employment boards seems to out that likely scenario, implying that Shadow Complex is a bona fide franchise for Microsoft Game Studios and Epic. Said listing specifically calls for a Lead Producer to "lead the publishing side of games made by Epic: Gears of War and Shadow Complex."
Additionally, Microsoft appears to be looking for more able bodies to join its growing pool of Project Natal and 343 Industries employees. Existing job listings call for everything from designers to engineers to even a few artists. Sadly, the company isn't looking for MJOLNIR armor models yet, but just in case, Microsoft, you know how to reach us.