Assuming that we could ever transcend biology, what would be the point? I've read Kurzweil's thoughts on this as well and thought the exact same thing: who or what would be around to appreciate or hate these self-aware digital entities (us)?
If a civilization retreated into a virtual reality beneath a planet's surface, then what interaction would that virtual reality have with the planet at all? Further, why would the death of the sun have anything to do with said virtual reality (which is now apparently decoupled from biology)?
I'm not saying that a technological singularity *couldn't* occur, I just don't have any idea *why* it would occur.