There’s no way to colonize Mercury, but human missions to and from the ‘dark side’ could be done. Not sure of the utility of it. Plant-the-flag is always a good reason though.
The first robotic Mars mission by SpaceX will be the first there and back by anyone. The ship will (one would hope) have its engines come back to life on schedule for a propulsive landing on Earth as early as 2028.
Sidebar, Buzz Aldrin’s idea:
https://en.wikipedia.org/wiki/Mars_cycler
Mercury.... well... if we ever run low on iron, silicates, pyroxene, or olivine... There is a region along the terminus between day/night that should be relatively balmy temp wise.
Considering those are the most prevalent materials in the solar system, unlikely.
Solar observatory? Break it down and use it as part of the Orbital (Iain M Banks) or a Ringworld (Niven)? Not nearly enough mass for a Ringworld... but enough for an O if the rest of the technological/engineering challenges can be met...
In out lifetimes? Best bet is an outpost on the Moon, Mars, and possibly some mining in the Belt.
Then Martian microbes will be released and will infect everyone on Earth. WE will then become Martians.
Future self plus “chickens” will be bigger.
https://www.threads.com/@bgwlldraws72/post/DFzitigxMHK/media