Mac on x86 made headlines a while back, with Apple stating that it was planning to use Intel processors in future Mac lines. Exactly when wasn't known, but it looks like we may see x86-based Macs as early as this January, according to Appleinsider. With the success of the iPod and related gear, the hype about dual-core Yonah processors and the relative performance level of existing Macs, they state that the Yonah is a good fit for replacing the 1.6-1.7GHz CPUs in existing Mac lineups. Though a lot more than that is involved in the change, it is a possibility.

”Looking ahead, Reitzes believes it is likely Apple will announce new products and content at its January 10, 2006 Macworld expo, with a possible introduction of the first Intel-based Macs. "We note that Intel will be introducing its dual-core “Yonah” processor in January (shipping now to vendors in pre-launch)," the analyst said.”
Speculation, speculation. It's unlikely that Apple will abandon their CPU hardware altogether, more likely moving to a split lineup. How will this impact Apple's future? Interesting stuff.