Hey!

I dont know if there are any official plans, but here's a stop-gap solution I whipped together, for those (like me) who really would like inverted dark default icons ;>

Looks like this:
http://artbykjell.com/krita/krita_workspace.png

Download here (EDIT: separate bundle, you will have to manage tags and stuff):
http://artbykjell.com/krita/krita_dark_default_brushes.bundle

Download for default replacement bundle:
http://artbykjell.com/krita/Krita_4_Default_Resources_darkmod.bundle
Note: I recommend you rename/backup the original bundle and then copy this in the default dir.
(C:\Program Files\Krita (x64)\share\krita\bundles or OS eq.)
Should work (tm) but who knows ;> Mess around on at your own risk! (separate bundle option above is there otherwise)

No, there are no plans at to to have dark icons for the brush presets.

Ah ok! More of a permanent solution then