I agree with what you are saying, except that you are misinterpreting the importance of Android to Google and in turn how touchscreens will be used with chromebooks. IMO Android will not remain a separate operating system from Chrome OS; it is meant to be an intermediate step to get to where Google wants to go. (When you think about Google's MO; this makes tons of sense. They are a fundamentally an internet-oriented company, not one that wants to build device-based operating systems in the long-term.) Instead, Chrome OS will incorporate much of the Android functionality and applications and eventually replace Android, for the kind of reasons you mentioned above. I think Chrome OS can and will compete in time with ALL operating systems across all form factors - desktops/laptops, tablets, and smartphones, mainly because it will incorporate the flexibility historically provided by Microsoft/Windows (but in the form of web-based applications rather than device-based applications) with the simplicity historically provided by Apple/iOS, using a client that is even thinner and more functional than what is provided on still device-centric operating systems like iOS. Chrome OS (or more broadly cloud-based OS) has the potential to beat BOTH Microsoft AND Apple at their own games, especially if/when the full Chrome browser has full desktop-like performance on today's mobile OS devices. If that happens, it will particularly problematic for Apple because they typically rely on making profits on hardware but computer manufacturers building Chrome OS computers will be able to undercut them on cost while likely providing an even better user experience.
One other thing I'll note is that because Google can develop applications and functionality for the Chrome browser and get user adoption (through Chrome installations on Windows and Mac OS computers), they don't need strong chromebook sales in the short-term to enhance Chrome OS and potential, future chromebook sales in the long-term. That is 1) a potentially powerful and almost unassailable position to be in (especially if their competitors are sufficiently behind them in developing a cloud-based OS and applications for that cloud-based OS), and 2) a very stealthy way to potentially get strong Chrome OS (i.e. chromebooks, chromepads - which will likely be sold in the form of hybrid chromebooks, and chromephones) adoption in a fairly short period of time.