A rating 400 over another rating is expected to win 92% of the games and 677 points over is 99%. So realistically, an engine would potentially be rated around 600-700 points higher than the highest rated human player, assuming the engine performed suffieciently well.
I guess theoretically you could have an engine that performed at that level over another engine where it would be much higher rated. Realistically, you would likely not get to that performance level as engines that strong are likely drawing too often to get ratings that high.
Computers have been dominating the Chessboard for quite some time now. Will we ever have candidates who can make "incorrect" moves to win a game against the supposed "Highest Ranking Possible". This threat will be filled with a ton of opinions, I know, and there seems to be no concrete answer. What do you think? Can you have a seemingly endless number of possibilities for winning against the toughest, strongest, most "correct" computer systems?