Apparently its already running, there are N900 testers tweeting about it as I type... and apparently BT mouse support is a go in Maemo 5 too...
N900's Gaming Prowess Makes Competition Quake!!!
We see games on mobiles everyday, but usually they're nothing close to their PC and console counterparts. But evidently, the N900 is no ordinary mobile device.
YouTube poster twaelti has given us a peek at the N900's graphical capabilities as well as the agility of the Maemo 5 OS. Showing the N900 running Quake III, the video is unlike anything we've ever seen on a mobile. I know we've seen ports of Quake and Doom on Symbian and Windows Mobile devices, but nothing as smooth and complete as this. In fact, I see no difference in performance between the original version and this mobile port. Evidently, the TI OMAP 3430 processor based ARM Cortex-A8 platform is up for the job in regards to graphical heavy lifting... .. . Read more: Quake III Arena on the Nokia N900 - full story
Very cool. I wouldnt doubt the N900 being capable of running Quake III and there already be a version available. The Pandora (Open Pandora) already has a version of quake 3 running adapted from hinkka's s60 port and it runs it pretty smoothly and fast at 800x640, having similar ( somewhat faster) hardware than the N900.