As with all rumors, please take this particular piece of news with a grain of salt. Since rumors about future Apple products are a dime a dozen you might want to take 2 grains of salt, however this particular rumor comes from a relatively reliable source (as rumor sources go): Apple is preparing to release their own take on a mini-notebook at the upcoming Macworld Expo.
If this particular rumor is true it seems that Apple's replacement for the long-defunct 12" PowerBook isn't quite as small as some might have hoped for:
“The 13-inch portable, which AppleInsider first detailed back in February, will mark the Cupertino-based Mac maker's re-entry into the sub-notebook market -- arriving in a form-factor that's approximately 50 percent lighter and strikingly slimmer than the company's current 15-inch professional MacBook Pro offering.
In achieving this smaller notebook footprint, Apple has reportedly adopted design cues that fall in line with the minimalist nature of its chief executive, including a bold move to omit a traditional optical disc drive from the aluminum-clad systems.”
We're still waiting for a true sub-notebook from Apple. Given that ASUS is one of Apple's manufacturing partners, we were really hoping to see some form of Apple UMPC based on a variation of the EEE design, but it doesn't seem like we're going to get our wish.