When will a rogue planet collide with Earth? Probably never again, although smaller objects like comets might hit us. However the future for Earth and life on Earth doesn’t look good either way.
For a planet to collide with another is like a bullet hitting a bullet. Space is big compared to a tiny planet, and the chance that a rogue planet might actually collide here is a long shot, even though we believe it may have already happened once.
It’s pretty unlikely to happen again because that was back in the day when the solar system was still forming and more volatile.
But what is happening is that the sun is running out of fuel. Every billion years or so it gets about 10% hotter as a result. We estimate that in 1.1 billion years it will be too hot to sustain life on Earth. The oceans will evaporate, greenhouse gasses will take over and Earth will become like Venus: too hot and raining sulfuric acid. All this happens way before the sun becomes a red giant and destroys Mercury, Venus and probably Earth.
So you don’t have to worry about that rogue planet hitting us. You have to worry about the future of life itself on the only planet ever found to have life.
Am I a pessimist or a realist?