Leaked images that appear to be from Microsoft's PartnerNet developer service suggest that Shenmue II may be heading to Xbox Live Arcade.
In the images the title "Project Berkley II" is shown on Xbox360Leaker's Recent Games list, obscured by a bright red "Leak" watermark. The icon for the game is the disembodied head of Shenmue protagonist Ryu, leading to the rampant speculation you're reading right now.
SEGA has yet to respond to requests for comment.
The publisher recently announced plans to increase its focus on digital downloads, so the prospect of Dreamcast games appearing on PSN or Xbox Live Arcade is very real, even if there's a good deal of scepticism about the leaked images in question.
The picture also links to a YouTube channel showing what appears to be footage from pre-release Xbox Live versions of Hydro Thunder 2 and Zeno Clash.
A video of gameplay from the upcoming Xbox Live release The Secret of Monkey Island 2: Special Edition appears to have been taken down from the YouTube channel at the request of LucasArts, according to postings on the channel's comment thread.