Also MS's decision to maintain legacy support is their biggest asset. If MS suddenly cut off a huge portion of their past compatibility, and hence established application base, then there is a MUCH bigger risk people will jump ship to Linux or Mac since they need to change up their apps anyhow. Familiarity breeds loyalty, even if sometimes begrudgingly.
They key is will the performance be reasonable on "mobile" hardware. The performance of portable hardware is advancing at a rapid pace but I'm not quite sure it's ready yet (even in a year from now) to run a desktop/touch merged Windows code base. That is where MS is taking a big gamble to me.