My point was that if you were to strictly just get the extra registers, I personally wouldn't consider the performance gain significant enough considering the broken compatibility and immense headache of porting everything. As far as I'm aware, AArch64 doesn't have compatibility with running a 32-bit OS, though I welcome being proven wrong.
I do understand the idea of doing doing this transition to 64 bit now before it becomes mandatory, but seriously, AArch64 should've been mainstreamed 4 years ago. I don't know enough about android to know how much it will be affected by this transition, but linux and Windows RT could suffer broken compatibility issues, particularly with closed-source software. It's already hard enough as it is trying to entice people to use ARM.