Hi Raoul

Greg Benford does quite a good job of imagining how diverse genus Homo might become after a billion years in his "Beyond Infinity" - he has hundreds of human derived species being revived out of gene vaults after a long period of stasis self-imposed by Homo superior. I think self-directed evolution might mean that something like the human form can be retained into an arbitary futurity, but that by no means implies stasis at the molecular level. I personally can imagine lots of molecular level machinery gradually taking over from old-style DNA/RNA - which is a bit too labile for high radiation environments and odd chemistry. Life extension would demand something more stable since cancer and aging are both caused by breakdowns in DNA/RNA replication fidelity after too many cell generations.

"Smart matter" cellular machines might be required in the long run, addressible by a body's operating system and able to undergo a degree of "morphing" into useful configurations - we would become our own tool-kits, assimilate silicates and metals, replace calcium minerals with carbon nanotubes, and augment biochemistry with higher energy density power-sources. Technology and biology will merge - if we are to survive in any kind of physicality in the billennia ahead.

Else, as you've rightly noted, we're just another mammal and fated to extinction.