A routine crew rotation at the International Space Station has taken on unusual significance: It paves the way for a pair of astronauts stranded for more than nine months to finally come home.

The SpaceX mission launching Wednesday aboard its Dragon spacecraft will bring a new crew to work on the International Space Station, as well as return the pair of astronauts to Earth.

NASA officials said earlier that Crew 9 — which NASA astronauts Sunita Williams is part of — will return only after Crew 10 ...