The world's most articulated Ultraman figure.
Wider angle of articulation for the back.
Improved neck position.
New extra part in back.
Updated effect parts.
Here's a little tidbit from Tamashii themselves. (I don't know if it's on purpose or not.)
If you can see the way Ultraseven's arms are folded in the above picture, you can see it's not possible with the current version of Ultraseven.
The small print beneath the above picture of the brothers over at the official site confirms an updated Ultra-Act Ultraseven as well.
The print translates to the brother's mantle, which is to be released in May 2012, does NOT support the 2010 versions of Ultraman AND Ultraseven.
So, unless they want to leave one brother out of their already advertised line of toys, get ready to see a new Ultraseven.