Since ARM processors were in mobile devices before Intel's, a substantial software base for ARM's processors was built up.
However, due to the way that the Google (GOOG) Android operating system and its programs are designed, instruction set is not relevant to
the majority of applications since almost every Android application is written in Java. Java programs are written in a high level language and
then compiled down into an intermediate form called bytecode. This bytecode is then, at execution time, translated into the actual machine
instructions by a virtual machine. This means that the only barrier to compatibility is having a virtual machine built into Android that can
translate Java bytecode into native instructions. Intel and Google have achieved this,
which is why software compatibility on Android is
essentially a non-issue. This is also why we have shipping Android phones with Intel processors in them today.
So the main barrier to entry for a new instruction set -- X86 in the mobile world -- is a non-issue on the target platform that Intel is aiming for
in phones. It also helps that Android's global market share is 75%. That means that Intel's chips could power the majority of the world's
smartphones without any technical limitations.
EDIT
Basically, its the same exact situation with ARM on the desktop: With so many apps written against X86, what are the chances it can make inroads? Not very good.
No it is not the exact same situation.
ARM have a far harder task in overcoming software incompatibility with x86 software, than Intel has with Android.