Rumor says that Android 4.4 will be optimized for ARMv8. However that won't really produce any sort of improvement since Android apps are bytecode in contrast to iOS apps which are native. The number of bits is irrelevant at the dalvik level anyways. Adapting Android wouldn't be that hard since the Linux kernel has been supporting AArch64 for quite some time now, a few core runtimes will need to be reworked but most of the userland stuff will pretty much remain the same.
So, Samsung are going to build a 64bit version of Android as well, are they?