I believe you'll notice that the photos of the E-?? do not have the little door-locks (for the memory slots and the battery) like the E-1/3 and Pentax K-10/20 have. I believe this means that any weather sealing in the E-?? will most definitely be somewhat compromised compared to the E-1/3 - and the Pentax.
Taking a close look at the following photo:
Indicates that the memory slot is sort of a two-action design:
1. Apply pressure to the middle of the memory slot door while...
2. ...sliding the door backwards
This minor change in the memory slot door may be all one might expect of weather sealing.
===
In addition to this, other photo enthusiast sites on the Internet indicate that the body is a metal subframe with a polycarbonate shell (like the E-4xx and 5xx). Several videos are out there showing people actually handling it. From those videos it appears that the E-?? is a little larger than the 520.
It could be that they've also slightly improved the articulating viewfinder sealing problem reported by some E-3 owners.
===
One small observation (for those who have enjoyed studying the photo): You probably have noticed that all of the buttons on the model shown at Photokina are quite clearly marked. The body looks basically 'ready for press'. It appears that many of the icons, buttons and other details are basically from the standard Olympus parts bin.... except for one detail that is strangely devoid of ALL detail and has clearly been modified from the standard Olympus parts bin...
... the dial on the left shoulder.
It is completely unmarked. If the dial is a 'standard' dial (like what's on the 4xx or 5xx series) then it has been intentionally made blank.
I am assuming this dial to be the mode dial - but the question is why would Olympus feel the need to obscure the standard mode dial if maybe there wasn't maybe something interesting to hide?
I would say that this new 'tweener' is a slightly grown-up 520 with one or two tricks up its sleeve that we are not aware of.