As long as there is no official release date set and no information being announced, it is probably safe to assume the 'next gen' game is at least 3 or 4 months from release. Other than that, we have little to go on for what state development is at, so a year is just as good a guess as 4 months.

The first 3 screenshots released (May '05) were from a test area when checking the game engine (ie the sign post doesn't necessarily give any info about the game), and another was released that Christmas (along with a wallpaper).

one (159KB), two (316KB), three (287KB), Christmas '05

The most recent screenshot (588KB) is on the 'Next Gen Game' page.

There is also a scan of a PC Gamer (Oct '06) half-page preview here, with a couple small screenshots.