Multicore is great a match for Android on ARM but there are no magic bullets for scheduling and I/O. The mobile phone market has validated both the multi, specialised core (CPU for managing the user, DSP for signal processing, etc.) and SoC (squeeze processing and radios onto the same component), which is why Intel and AMD are playing catchup with the unified architectures.
ARMs smaller, weaker cores offer greater efficiency for the majority of tasks, whereas as Intel's larger, stronger single core shines at individual disciplines. If it weren't for the GPU Intel would shit on ARM for rendering websites which is a surprisingly complex task. But the GPUs are there offload the rendering to.
Intel's advantage in chip-manufacturing is essential to be able to compete in the mobile market. But, as long as its unit costs stay at least a factor higher than the competition, it can't afford to maintain that advantage forever. And it's not even as if the competition is that far behind with the move to 32nm already happening.