It would be a good thing to have a brain that is a robust collection of artificial machinery when such a thing becomes possible, as the present evolved biological human brain is short-lived and frail in comparison to what could be achieved with a mature nanorobotics industry, capable of producing robust nanomachines that replicate cell functions. But how do you move from a biological to a machine brain without destroying or merely copying yourself? All of the obvious, easily envisaged methodologies are variations on the theme of destructive copying, in which you die and a copy of you continues.
This continuity of the self through an upgrade of the physical structure hosting your mind is a popular topic in the longevity advocacy community. Pretty much everyone has written on the subject at some point in time, despite the fact that it's definitely not the next thing up on deck in the march of technology - the first order of business is to develop the means to repair aging in our biology, to give us enough time to live into a future in which things like brain upgrades are possible.
Later in the piece quoted below the half-brain methodology is discussed. This is one of the earliest attempts to produce a physically realistic method of progressive brain replacement that is at least one step less fatal than all-in-one-go destructive copying. But I think that it is still undesirable: hauling out and replacing large chunks of the brain at a time is still functionally destructive to the self if the chunks are large enough. The safest approach is to scale down the replacement to the level of individual cells, proceeding at a pace similar to the natural processes of cell replacement in the brain.
I love life. And so the prospect of indefinite life extension is very attractive, IMO. Then again, seeing as how I wish to live much longer than my biologically-fixed clock dictates, to simply make a copy of myself to live forever, but not actually myself, just doesn't cut it. I would never destroy my brain and let someone else be me for me. If I'm to achieve indefinite life extension, then I want to do so with both my physical and functional continuity still in complete operation. Without one, the other is completely irrelevant.
What is physical and functional continuity? Functional continuity is basically the stream of consciousness which makes you...well...you. "Destroying" functional continuity wouldn't necessarily do anything to you, nor would it remain destroyed, per se. When we're going through REM sleep every night, our functional continuity fluctuates on and off, only to be completely restored the next morning. Yes, your consciousness before sleep was different from the consciousness you now acquire after sleep, but you remain yourself - you're still self-aware.
So what about physical continuity? Physical continuity is very important - much more important than functional continuity. Physical continuity - using as simple an understanding as possible - is essentially the brain and all of its synaptic operations. To destroy physical continuity would be to destroy the brain. Thus destroying everything, including the functional continuity which comes along with it. You can destroy your functional continuity and still have the chance to regain it so long physical continuity remains intact. The contrary, however, would be the end of yourself in its entirety.
Thus bringing us to our current dilemma of mind uploading. How are we to achieve mind uploading without destroying physical continuity in the process? To simply "download" everything within your brain and upload it into an artificial brain, while functional continuity is being streamed, physical continuity is being replicated, not maintained. Essentially you'd be partaking in a really cool process of cloning. That's it.