DPReview, CNET and some other sites claim that the newly announced Canon ELPH 500 HS (IXUS 310 HS in Europe) camera has BSI sensor. The 1/2.3-inch sensor's resolution and speed is 12.1MP/3.4fps and it is capable of 1080p24 video.
However, the official Canon PRs do not mention the backside illumination at all. They only talk about "HS System" that excels in low light: Canon US PR and Canon UK PR. It would be strange if Canon really hides BSI feature under HS title.
Thanks to JB for pointer to the Canon announcements!