Even that would not be conclusive. Each person has to take the pluge for him/herself. It's like the believe of life after death, essentially. No way to prove it except by going through the experience yourself. All other information about survival of consciousness is second-hand. Even recall of human memories memory input to a black box could be a case of rote recall without consciousness.
It's just another way of reframing the Cartesian dilemma. Whatever the case may be, my personal view is that indefinite lifespans will come around before total upload is possible, so the question is largely moot. As for total upload, there will probably be a merging of man & machine by increments anyhow, so when it finally comes along it won't seem like such a leap.
PS. I'm not saying everyone will undergo said merging. Perhaps even only a select number of technophiles. Whatever the case, there will probably be Luddites who will resist such technologies for a very long time to come.