with the possible exception of finding an example of panspermia (common origin) life in our solar system.
I would love to proved wrong though. Keep looking.
I think one possibility that might be within the 20 years would be a Kardashev Type III in another galaxy. These are relatively easy to look for and allows a search to cover billions of years of universe existence. 400 billion galaxies times 200 billion stars roughly - that is a lot of chances to find one intelligence that spanned a galaxy.
The problem with primitive life on a exoplanet is that it will be exceedingly difficult to distinguish it from some sort of exotic chemisty. I mean we still fight about Venus and Mars and the possibilities that we missed something and the tantalizing chemical indications of something. Make that discovery 1,000 light years away, and you can see the addition problems.
One of the gas giant ice moons seems off the table for detailed exploration in the next 20 years (punching through the ice). Perhaps we will get lucky with a scoop mission on Enceladus or Ganymede, but I have my doubts about those even launching in the next 20 years.
Type II structures around one of the exoplanets - a possibility but it seems less probable than a full sky survey of Type III in another galaxy.
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