Something else people fail to consider...
Why would a consumer buy an iPad instead of a Nexus 10 (or similar) when they already have an Android phone? The answer is ... in most cases, they wouldn't.
Last quarter, Android topped 75% market share of all smartphones sold... Apple fell below 15%. That may be a serious problem for Apple's future.
On a related note... Windows 8 will probably work in the exact opposite direction. The Windows 8 tablets will make some headway (especially in the corporate world) and drive sales of Windows 8 phones.