"What if the A9 out-performs Intel equivalents, and Apple decides they want them in their Laptop and Desktop systems?"
That's a matter of when, not if. Apple likes the control the entire widget. They will.
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"The performance gap between ARM and x86 is huge."
CURRENTLY, that is true. You're assuming that will always be the case. For all we know, in 2 to 4 years, that gap might not exist.
You think Intel just gonna sit there and wait? No.... As i said, A7 is merely equivalent to my 06 AMD Athlon X2. In four years, yes, you can build a home computer with ARM processor, but that only gonna happen when software developer starts to jumping on ARM. Look at currently Windows RT app situation, it does not look like app developers want go all out for ARM platform.