A new way to color and manipulate your mesh,
A virtual air gun blower that will blow your polypaint like aquarell with acumulations settings at the end etc. (would be cool if there are also some blending effects are incorperated)
And for blowing your 3D mesh your can spray your mesh around
A cool new way to mesh insert,
That will search all your meshes in your database,even the nested ones in the IMM brushes,
So you can quickly get all the meshes in all of your Z Libs
Place a dot on your mesh ,and after it will loop through all your meshes even the nested ones in the IMM Brushes,
So you can quickly add a mesh on that point (pivot) or swap another one when you click on the MI Marker.
A new setting to color with lightning information,
So you can play with lightning information and that burn that into your model,
Even the adjustment settings that will do a complete overlay effect in zbrush will be taken into account
A new setting to morph between multiple versions of your meshes,
To quickly see some cool morphing effects or just to create a whole new hybrid of two versions.
A new random blob (splat) Setting that will use an algorithm to generate a random blob for nice painting settings.
A visual tool that can be shown in Z Brush like a real rake tool etc that will follow the normal
It could be handy for some people
(But have a setting that can turn it off,I dont think I would use it much though,I like my workspace clean)
But could be handy for traditional artist that want to see there tools maybe
A new GOZ feature that will use a special camera in your favorite 3D program,
That will addept to your Z Brush canvas setting Scale and absolute system,
So you can use Z Brush materials and all your 3D program materials,
So you can blend between them.
Maybe easier to addept to zbrush absolute system ,and create a special camera in a 3D program.
A cool new Skin Based Morpher,
That will swrinkwrap around the first model, than used on a other model with different topo (but the skin morpher stays the same topo)
And after the second skin wrap , the skin morpher will be used as a morphing helper to morph between the 2 versions
A Z Brush based 2D morphing helper,
Like the one in flash (vector based), with point helpers to help the process and fine tune the image morphing.
It would be cool to have a new format for it ,so Z Brush reads a morphed alpha.
So you can use pen pressure with it etc.
A heat gun to liquify your model in some points 
A new curve setting,
For when you have a high density curce, a new setting that will use point on the same curve (type in),
so you only have a few points for easy manipulation (smooth bezier curve like in max)
Off setting curves could be cool
With attachment,follow,banking settings etc
A cool on the fly window that will take a image from zbrush,
and does a grayscale ,and displacement manipulation that you can do on the fly.
A wind force system to go with the fiber mesh could be cool.
A way to make curves in Z Brush that can snap to Z Spheres , and follow it.
When connections and datastreams become a possibility, you could swap in Pixoltown to a live animationfeed
Or stay with preset animations if you want.
A new type of skin is placed over the mesh, that can handle dynamic painting types.
That you can burn in the underlaying mesh through polypaint or flooding it in Z
Live commentator and judges for when the speed scult battles begin.
A golden ticket can be found somewhere in Pixeltown, the lucky finder could get the winning Art battle mesh ,completly rigged, so they can use it right away in Pixeltown.