The weight question is both impossible and easy. The impossible part: it depends on what makes you happy: a light bike, or having everything you could possibly need. The easy part: you're planning a year long tour in 2010, so you have plenty of time to take a weekend tour and see for yourself what you'll need. Of course it depends on the place you'll be heading, so although I think Ms. Machka knows her stuff you simply can't apply a formula - not if you're needing 10 pounds of water to make it to the next spigot.
In general, however, I cannot recall meeting another cycle tourist complaining that they didn't bring enough, and many that wish they'd left more at home. Many end up mailing stuff home after they didn't use it. So pack light. I don't wear cycle clothes, and that helps - no extra shoes and pants and shirts. I've ridden from Tucson to Death Valley with 15 pounds of gear - not including food and water.
It felt wonderful.
Yours,