Speculation: how about a full frame Fuji camera with M-mount?
Ok, this is not a rumors, just a speculation based on the latest post from Brandon Remler (who works for Fujifilm USA):
"Leica can have the 24 x 36 arena and stay around $10,000 (with 35 2.0 lens) vs the APS-C X100 at $1200. (Did you know the Leica M-lens mount is not a proprietary mount and thus anyone can make a mount to use their lenses? (I think at least - correct me if wrong- thanks) I've seen it on the Minolta CLE - Hexar-RF, Cosina, Rollei 35RF and Zeiss Ikon, and they sure do have a bunch of neat lenses over the past 55+ years, see list way down since 1954)."
and then later in the post:
"When the X100 has a little brother (Sept 1) and it yearns for a big brother, the decisions will be even tougher!"
Fuji X100's big brother? M-mount? I hope this is more than just a speculation!
BTW, there is a long list of Leica lenses at the end of Brandon's post.