Its very predictable as to how this election is going to turn out. All one has to do is look at the demographics and how they vote. Blacks and Hispanics have favored the Democrats since 1980. The Whites have favored the Republicans since 1980. Since the Black Americans will overwhelmingly vote for Biden, it really depends on how the White population of the United States votes, since they are the least likely to mail their vote in (poor communities are most likely, and are composed disproportionally of Blacks and Hispanics).
Trump will be leading by 12 AM November 4, and will declare victory. Once all the mail-in votes are tallied, and Biden catches up, and surpasses Trump, the GOP and Trump will claim the election was rigged, and that the mail-in votes were fraudulent. AG Barr will back him up. There is a chance that Trump (with the support of the GOF and the AG) will refuse to leave office.
This will take us well into late November, and at best, will be held up in court longer than the 2000 election result was (probably well in 2021). A worst case scenario is the result of the election could spark a civil war in the US.