In all honesty, we really don't need 64 bit machines, by going to 64 from 32 it has allowed programmers to become very lazy and messy with their code, if they would tighten their programming up, we would never need more than 32 bit and 4 gb of memory to do the most complex equations developed. But as things move along, we will see 128 bit processors become the norm, not in anyone that posts here's lifetime, but it will happen. But if you think about it a 32 bit processor has the capabilities to address 4 GB of memory in one operation and a 64 bit processor can address, wait for it.......16 exabytes! But also take into account, on many tasks a 64 bit machine is actually slower than a 32 bit machine and if we made the jump to a 128 bit machine, it would slow down even more. What we need for faster processing, is people to start writing code for the lowest common denominator, which is 4 bit code to run on 64 bit machines, so there is no wasted code in there. When your machine is taking up a 100% of your resources, it is running dirty code, and it continually re-processes it to try and execute that code that is mixed in and no good.
I know, way to much information, but the possibilities are endless with computers the the limits are once again, the human factor that writes the code!