You can't extrapolate future computing improvements based on the past, we are hitting physical limits now and in 50 years may not have computers dramatically faster than today.
I don't believe we are anywhere near the physical limits of computing at all; the laws of mathematics, physics and information theory give us an enormous upper bound on capacity. There are technologies like quantum computing we haven't even started to scratch the surface of, and our knowledge of nano-scale engineering is still very much in its infancy. I would be very surprised if in only five years computers were not dramatically faster, let alone 50.
