How about a dual-booting tablet that runs both Android and Chrome OS? When you attach an external keyboard and boot into Chrome OS it basically becomes a Chromebook. How cool would that be? Quick boot-up time is a frequently touted benefit of netbooks, so this would work out well.
Optimizing the experience based on whether the user is using a keyboard or just the touchscreen seems like a win. Using Chrome OS in the former case and Android in the latter would be an obvious way to accomplish that.
Note: According to a somewhat recent CNET article, Google is actually working on a tablet version of Chrome OS.