As the title says. Let's say, Cleopatra never retreats, so neither does Antony, and, though victory at that point in the battle was perhaps improbable, it would not be impossible, so let's say that the Octavians and Agrippa are forced into retreat and Antony has taken a victory with heavy casualties.
What happens from there? Octavian has not gained the decisive victory that effectively ended the Republic's final civil war, and his navy has been whipped. Antony, meanwhile, remains in a dangerous position.
Discuss the possibilities.