How will the solar system change in the future?
The solar system is currently quite stable. The sun is in the middle of its main sequence life. It is getting hotter slowly so planets will experience additional heating.
In about 4 billion years, the Milky Way and Andromeda galaxies will collide. it is possible that during the collision another solar system may come close enough to perturb the orbits of planets or even eject planets from the solar system.
There will be a big change in about 5 billion years when the sun runs out of hydrogen fuel. The sun will then expand into a red giant. At this stage, Mercury, Venus and possibly Earth will be absorbed by the sun. At the same time the other planets will get warmer.
Ultimately the sun will collapse into a white dwarf. The remaining planets will no longer receive heat from the sun and will get extremely cold.