Going on nothing more but rumors, there has been speculation that Asus has been preparing an Android-based netbook. Naturally, the company wasn't forthcoming on whether or not this was true, until just now. This will add a third major OS into the mix of Netbook software, on top of the specialized version of Windows XP and the Linux distributions currently used by outgoing products.
One of the benefits Asus may be able to play up is the fact that Android has been built for mobile, low-power hardware. Given the profile of the current Asus netbooks, I'm expecting that we'll actually see the same hardware being used. If not that, then Asus could use an even more slimmed-down unit specifically for the Android OS.
While system responsiveness and functionality could be key for adoption, Android is nonetheless poised to face the same adoption issues as Linux considering a majority of people still prefer Windows on netbooks. With an estimated release before the end of the year, it's also expected that Microsoft will have delivered a supposedly netbook-friendly Windows 7 OS by then.