The “notion of the App Store” existed long before Apple was on the scene.
Blackberry had an App Store
Plam had multiple app stores, Handango being one beside the main Palm App Store
Windows CE, Pocket PC had several.
Etc.
You should clarify why Apple succeeded where others have failed as the “notion of the App Store” was not the reason.
Of those, Handango is really the only one that fits the bill. BB didn't even launch theirs until years after iPhone. Windows CE and Pocket PC were mostly sideloading unless you count the carriers who insisted on being the gateways to their horrible software. You couldn't even put Microsoft's own software onto a Windows Mobile phone without loading a CD then moving over the mobile executables.
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Whats going to really hurt the iphone is that smartphones have become a commodity and thus will have to compete on price. Android has gotten real good lately and the Chinese OEMs are coming out with great phones for $200 to $400. Apple and and the Koreans (Samsung/LG) can't compete on a price like that.
Remember Sony? Toshiba? Panasonic? RCA? Magnavox? They were big electronics companies too but the Chinese came in and ate their lunch. TCL, Huawei, Vizio, and other Chinese companies will take over in the next 5 years. Watch and see.
One thing you should take note of here is that none of those companies were even close to where Apple is right now with iPhone. There's definitely a possibility of this becoming the case but I don't see China knocking out Microsoft or Google here either, because it's just not as simple as it was with a pure hardware product. Also, it's South Korea, not China, that ate those companies' lunch.
And Vizio is an American company.