It's not the brain that I'm worried about losing, it's the body. The ship of Theseus imagines I am replacing parts with nigh-indistinguishable parts. There is a fundamental difference in going from squishy biology to program in the cloud. I'm not even sure it's possible for a machine to have a subjective experience like a human's without the squishy meat parts, and I doubt we'll learn enough to emulate those parts successfully for a good while. I'm pretty attached to my hands and face and would probably be very unhappy if I lost them.