The capability of each phone is entirely different, the user interface of each phone are very different, how each phone works is radically different.
HTC Incredible vs. Nexus One
Just understand that you are making a future prediction, that's not the current reality.
Nice, obtuse post.
Of course predictions refer to the future. Do you normally predict the present?
And sure, the Nexus and Incredible have different desktop/homescreens, but that doesn't mean the Android SDK is different for each phone. If I change the icons and background on my OSX desktop does iWork break? Of course not. The underlying system is the same.
Sure, Android is open source, but so is the OSX kernel. People could of course design a bunch of non-standards based versions of Android where no existing apps would work, but why would they?