Microsoft would disagree with you. They've been selling tablet PCs for a decade now.
What's completely flawed about your argument is that you somehow forgot that the iPad is the competition for the "other" existing tablets and in fact the iPad is the last to come to the market so if those "other" tablets couldn't make it in the first place you can forget about them stealing much of the iPad's market unless they steal the iPad's functionality and at that point they'll be nothing more than a worthless clone that's "LIKE" an iPad.
Did either of you even read the article that was quoted? I ask because it doesn't mention microsoft. Nor does it even qualify the statistic as to what is considered a tablet computer and what the marketshare for anything other than Apple vs Google.
HLdan - Flawed is believing any statistic just because you happen to like the outcome. This statistic - as I stated - is pretty meaningless on it's own. Let me know (either of you) if you find the actual source analysis from "Strategy Analytics" which this "article" was based on.