Canon Rumors has a post that claims the Canon UK site temporarily shared Canon 5D MKII firmware update information, before pulling the web page. CR says the info posted was:

Features
Live Histogram for Video
Sound Level Control
24p/25p

The release date was marked as March 17, 2010. So we’ll soon officially know if these features make it into the final firmware release.

UPDATE: Apparently there was a presentation today in Poland where Canon 5D MKII new firmware features were discussed. In picture from the presentation, there is a list of features that will be included (assumedly in the next firmware update). They include:

NTSC Modes:
1920×1080 @ 30fps
1920×1080 @ 24fps
640×480 @ 30fps

PAL Modes:
1920×1080 @ 25fps
1920×1080 @ 24fps

Adds manual sound recording functions (64 levels) with audio meter.

Adds histogram display (brightness or RGB).

Adds shutter-priority (Tv) and aperture-priority (Av) exposure modes.

Changes the audio sampling frequency from 44.1 KHz to 48 KHz.