I have an iphone 4s, an ipad 2 and 15" MBP also I have a Windows 7 PC with 22 inches LCD monitor so I don't think I need a BIGGER iPad!
Looking from a manufacturing process, it could also mean easier work, and chances to have better precision and yield, since the sizes are perfect rounded numbers.
For me, the bezel is barely wide enough - I often find myself accidentally clicking the side of the screen when I'm trying to hold the bezel.
I wouldn't mid an iPad with a full 8.5x11 screen for reading, docs, etc - but I think it'd have to be a bit thinner and the same weight as now (or less) so I'm guessing that's a couple years out.
I hate to say this...but why not get a MBA 11"?