[imoverclocked]

There may be other cool tricks that we haven't thought of too. No reason that we need to make things bigger and colonize the galaxy if we figure out something neat that is smaller instead! eg: Maybe we figure out that we can accelerate small telescopes to some significant fraction of the speed of light for an observation. Or perhaps we find some other neat physical phenomena to manipulate incoming light.

The cool thing about scientific and engineering progress is that we can't know what we will discover and develop. 200 years ago, we started having electric lamps. In just 100 years time, we have gone from computers being fringe and folly to them being integrated into places they don't even need to be for sheer convenience. Assuming humanity makes it another 100 years and continues to advance technologically, things we only dream of today could easily be so common-place that people can't imagine living in the current dark-ages of technology.

Also, 100 years is a cosmic blip! If we are thinking ahead to the point where we can't see things in the universe that we can see today, humanity itself will likely not be recognizable from our current vantage point... assuming it exists at all.