The issue goes up to the Supreme Court, which unlike the 2000 election does not decide the election in favor of the Republicans. However, it indicates again that the December 14 Electoral College deadline must be met; that the president’s national security powers legally authorize him to investigate potential foreign country intrusion into the national election; and if no Electoral College slate can be certified by any state by December 14, the Electoral College must meet anyway and cast its votes.

The Electoral College meets, and without the electors from those four states being represented, neither Biden nor Trump has sufficient votes to get an Electoral College majority.

The election is thrown into the House of Representatives, pursuant to the Constitution. Under the relevant constitutional process, the vote in the House is by state delegation, where each delegation casts one vote, which is determined by the majority of the representatives in that state.

Currently, there are 26 states that have a majority Republican House delegation. 23 states have a majority Democratic delegation. There is one state, Pennsylvania, that has an evenly split delegation. Even if the Democrats were to pick up seats in Pennsylvania and hold all their 2018 House gains, the Republicans would have a 26 to 24 delegation majority.
This vote would enable Trump to retain the presidency.