Mark Rein from Infogrames has updated their forum with following news:

We understand you are anxious for the demo but posting "where is the demo" threads here won't make it appear any sooner. When we think we're close to the demo (i.e. within 5-7 days) we'll let everyone know officially through this forum. We're not there yet, we're still more than a week away. We could be more than two weeks or even more than three weeks away. We're not holding out on people, we're just not done with the game yet and although a lot of the game is coming together very quickly we still have no 100% (or even 80%) accurate way to predict exactly when that will be. I promise the development team is working very, very hard to get an awesome, polished UT2003 in your hands. The demo will be released when we think we've got all the major functionality of the game complete so that the feedback from the demo can be focused 100% on things we weren't already aware needed to be addressed.