I think a lot of transhumanists have an escape-fantasy where they get to take their existing mental-motions and place them in a new body sort of without consequence, with the idea that this will heal them or be super fun or whatever. While I think this will be possible, I expect it to be extremely traumatic, and that people who are investing into their sense of embodiment and health now will be far more ready to reap the benefits when body modification technology gets much better.

As it stands, I think ripping the mind out of the bodymind and trying to throw it into a new "shell" ignores the fact that the body is also part mind, and that the bodymind is not two things. It is one thing!

In many cases, I think you actually will be able to sever the body from the mind and go into a new body fresh. But I don't think this will work for everyone, and I think people who have some sort of comfort and appreciation for their existing form will be much more resistant to the body-double equivalent of organ rejection.

Ultimately, the lesson I'm trying to point at here is pretty mundane. Even if you plan to leave your body once the singularity hits (a type-error tragedy if ever I've seen one...), becoming embodied now and learning to love your form will serve you in your long-term goals. It may even help you enjoy your pre-singularity time a little bit more while you're still here.