A new property named or codenamed Osiris seems to be in the works at Ubisoft Montreal.
NeoGAF users turned up a "rough-cut demo" for "Ubisoft's Osiris".
The proto-trailer features motion capture which looks very similar to behind-the-scenes footage of Ubisoft Montreal's studio, and the trailer bares the legend "from the studio that brought you Assassin's Creed".
The video is posted to the Vimeo account of one Mark Kilian, and is flagged as "commissioned by Ubisoft Studios (Montreal)". It was posted five months ago, apparently as part of a portfolio.
Industry sleuth Superannuation speculates the video may explain rumours from last year about a Prince of Persia reboot; an ancient Egyptian setting, as suggested by the title, could be mistaken for Prince of Persia's sandy fantasy setting.
Don't expect that video to last long if it is legitimate; go forth and watch.