Not that we wouldn't eventually expect a 2.6GHz MacBook, but this promo on Apple's Hot News site which references a new model of the laptop (which right now only reaches 2.2GHz)? We're thinking typo, not premature announcement.
[Thanks, Matthew and fr]
http://www.engadget.com/2008/05/11/apple-promo-references-2-6ghz-macbook/