The engine is technically called 'Source', anyways; plus Valve had already said they'd build HL3 on Source (to state it wouldn't take as long as 2). I would expect the Source engine itself to be ported to the next gen consoles, though; it's economical sense to do so.
Bear in mind you can't tell the number anyways, because it's a compressed JPG. Because JPG matches, IIRC, regions in the image to a table of set pixel patterns when compressing (not to mention any noise data in the image before compression), you probably won't get a reliable image from scaled up images; just look at how indistinct the letters in 'Half life' are, for example.