Apparently (I read this yestarday but can't find the link, I'll repost it as soon as I find it back) those are
recommended hardware requirements, not minimum requirements. This was clarified in a note by Google inc. itself, so Android 3 (Gingerbread) won't be limited to Nexus 1, Desire, Evo, Galaxy S and Incredible only.
EDIT: ok, I read it on Eldar Murtazin's twitter:
http://twitter.com/eldarmurtazin/status/17550974090
He is Mobile-Review's editor and the one who first gave the news about the hardware requirements of Android 3.0