Unfortunately the simulated classical humans in your Matrioshka Brain will want to mine Bitcoin, which means that our digital descendants will have to become a true interstellar species anyway in order to convert the Laniakea Supercluster into coin-mining computronium.
I grant that. But why would that keep us from pressing on?
If we have more resources in general, we will also have more resources for interstellar adventures.
We already have quite a lot to exploit in the region around us.
We assume we understand our future wants, needs, costs, and capabilities. (Granted, any future thinking is also subject to this, including my own.)
I don't disagree.
> We assume we understand our future wants, needs, costs, and capabilities. (Granted, any future thinking is also subject to this, including my own.)
Even if 99.99% of people are content with what the solar system has to offer, there will still be billions left to go and explore and settle outside for whatever needs and reasons they have. Even if those needs are imagined, or the reasons might be purely ideological or religious.
> But I think that assuming we'll want to send lots of entities vast distances in space and time might be a lot like thinking we'll have flying cars.
If only a tiny fraction of people will _want_ this, that's enough.
If we can harness all of the energy and mass available in our solar system, we [1] can likely compute more than several galaxies full of classical humans. We might even begin to test the edges of physics.
Maybe we don't need to go anywhere at all. Maybe we [1] have all we need right here to become literal gods.
[1] Our digital descendants. Humans are very much fit to the gas exchange and metabolism envelope of our gravity well.