Android will have to move to 64-bit sooner or later, because some of the high end devices have RAM creeping uncomfortably close to 4gb. The Moto X, Nexus 7, and pretty much every other flagship phone or tablet all have 2gb RAM. The Galaxy Note 3 has 3gb RAM. A transition to 64 bit would happen primarily for memory reasons, not for some magic performance increase.
I don't argue the fact. I argue the attempts to downplay Apple's move to 64-bit architecture and it's benefits.
Here is something to think about:
The 32-bit Windows Server 2000 Datacenter Edition could address up to 256GB RAM. How did they do it? 48-bit addressing (effectively using 38-bit physical address lane), similar to the way the Intel 80286 (16-bit) processor was capable of addressing up to 16MB RAM (24-bit addressing; 16-bit allows for only 64KB).
The 32-bit/4GB barrier could be crossed by paging the RAM in multiple 4GB pages. That, of course, requires OS support. In such a scenario, the OS could support more than 4GB RAM. Each application will be restricted to 4GB linear address space, but multiple applications could be hosted in different areas utilising all the available memory. Programs that require more RAM, should support paging.
So, 64-bit architecture is NOT a requirement for supporting more than 4GB of RAM. Due to the complications around paging+memory virtualization in the software and system libraries, however, that approach is generally avoided.