forthesakeofsin
In order to gain immortality humans would have to give up all earthly pleasures. Food would be pointless, sex would be non existent, we wouldnt apreciate life for what it is. However immortality is only a few decades away with prostethic limbs and organs already being created. The prostetic body is next.
The problem is brain decay. You can create all the prostetics you want, but eventually your brain is going to fail. So unless we manage to figure out how to transfer sentinence into an artificial brain, you're still as good as dead.