ah the technological singularity?
well yeah I wouldn't mind that
and then there this http://2045.com/
Too many flaws in that idea, simply transplanting a brain into another more suitable body/avatar won't change anything, the key to longevity is to prolong the division of cells, once cells stop dividing then bodily functions cease, the brain also depends on this. The brain is organic and thus it will be subject to deterioration. Plus brain transplants are almost impossible (if I gather correctly)
So basically we need to find a way to keep the cells dividing, once we figure that out we won't really need an avatar, we could just remain in our body.