My bet is, over time, the OS will become much less of a deal. The more you move off of the device and onto servers or the cloud, the less relevant the OS becomes.
OS will be more of a hardware bridge to cloud services. For example, if I need recording music with my third-party audio controller, the browser must recognize it as an input device and take advantage of all of its features.
This will be the next chapter of OS-war: make the browsers smart enough to take advantage of external IO devices. Javascript will have to support a kind of hardware abstraction layer (it already has improved graphics support in HTML5 but still lacks a lot of audio support, scanner, video and photo devices).
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Sounds exciting for those waiting for iPad 3, BUT, coming from someone who currently does not own an iPad (me), I will be keeping my eye on the Clearance section once these launch in hopes of scoring a deal on the iPad 2.
iPad 3 looks like a great tool for photographer presentation, viewing and mobile editing. For all other uses, iPad 2 is perhaps a decent content consumption device for the next 2 years.