end with us leaving our biological systems behind all together
so you are actually talking about something "post-biological" - ... I can't see it yet. I hope we can work things out on this planet.
IMO it all comes down to how artificial intelligence arises. If we can create non-human intelligence that supercedes our own, then I think we have little choice but to be left in the dust. Non-biological intelligence won't be tethered to us for long, and will probably start doing things for its own reasons. However, that is an interesting situation in of itself: we have evolutionarily ingrained bahaviors that mix with our intelligence. Non-biological intelligence will not. Therefore, its motivations might seem very alien to us.
Becoming post-biological does not mean we will leave this planet. But it will enable us to inhabit multiple planets (and multiple star systems). Unless... transcension.