Bitness is more about per-process address space than total RAM. For example, a 32-bit process could not memory map a file over (somewhat less than) 4GB in size, while a 64-bit process doesn't have this problem. Wanting to memory map large files is something you could do on just about any current mobile phone.
Also think Moore's Law. Current phones are sporting 1GB of RAM. It will just be a few years before they exceed 4GB, and it's easier to get the software support ready now.
No it won't be. Some of the high-end phones already have 2 GB, and next year it seems they'll have 3 GB of RAM. So 64 bit is arriving just on time in 2014 (although Cortex A15 supports extension to 40 bit, but using that may be a bit messy):
Also think Moore's Law. Current phones are sporting 1GB of RAM. It will just be a few years before they exceed 4GB, and it's easier to get the software support ready now.