Dual booting may still be offered, these are just demonstration models and Asus has been known to make last minute changes.  While mind Windows 8 will be the main OS regardless, being the more powerful desktop OS and the main reason why they added the extra GB of RAM.

However, dual booting is not something usually given to any system.  It’s pretty rare in fact for it to be offered and usually has to be done by end users.  Thus why there are so many how-to’s on doing it.

Mind there’s not that much space on these devices and Windows is going to be taking up a large portion of that space.  So the option of a additional OS would have to be balanced at what’s left to give end consumer to store their data.

There’s also the matter that on ARM MS isn’t allowing secure boot to be disabled.  So only OS with validated digital signatures will be able to work on the same system.  Though Google is probably already in the process to getting that done, it just cost a fee for each kernel and driver being certified.

The developers of Fedora Linux for example recently decided to do just that to make sure that distro can be run on any Windows 8 system.

While Asus is pushing Bluestack service for their Ultrabooks, with the first 6 months free.  Since touch screens are starting to be offered for them and like RIM’s move to let the Playbook run Android apps it helps compensate for the lack of Metro apps as it takes time to properly develop a new app ecosystem.

Though that’s probably a good reason for them to add Android to the Windows RT systems as Windows RT has no legacy support and would depend entirely on Metro apps and the few desktop apps that MS itself provides like Office and IE.