Some artwork posted by Great Graphics (since removed) includes a poster of the skin-headed protagonist from the Hitman franchise and a 2011 date. Great Graphics worked with IO Interactive on Kane & Lynch 2: Dog Days, so it doesn't seem implausible that they'd be working on promotion art for a new Hitman too.
It's worth noting that the posters are listed as concepts, and may have no relation to a real product at all. Still, they're worth a look. GAF's got the set.
Update @ 11:44BST - IO Interactive's Tom Stratton has responded: Unfortunately, the concept art was created as part of a portfolio. [It was] intended to showcase an artists style or method of work and does not represent any new Hitman game. We still reckon there's a new Hitman in development.