A tremendous article over at Xbox-Scene has laid out the Jasper board for the Xbox 360 (the board that takes over from Falcon) and seems to indicate that Jaspers are now cropping up in retail boxes.
Stand-out additions include the fact that "the onboard flash chip has grown from 16MB to 256MB. Microsoft included internal memory storage, so the Arcade SKU now ships without (external) Memory Unit and the new NXE dash will install fully on the flashchip (rather than requiring a HDD or external MU). But the internal memory can also be used to store gamesave data, XBLA games, videos or whatever."
One way to check? Well, have a look at the power lead. According to the article: "The new power supply is now 150W (25W less than those used with Falcon boards) and the plug has of course been changed so u can't plugin this PSU into an older motherboard."
See the full piece at Xbox-Scene