The context suggests that Jesus was praying for His executioners and for the crowd that tagged along to view a public execution. I would guess he was not praying for the murderous scribes and Pharisees who planned His death. He had already said to them, “You will die in your sin” (John 8:21) and “you belong to your father, the devil . . .” (John 8:44). Their fate was sealed.
In Peter’s first sermon (Acts 2), he included the entire nation in the crime, and he urged them to repent, be baptized, and save themselves from “this corrupt generation.” In his second sermon (Acts 3), Peter said he knew that they had acted in ignorance, “as did your leaders.” But not all their leaders acted in ignorance; the principals were moved by envy and malice.
In any case, Christ’s prayer was answered for those who responded to the gospel, as is clear from the first few chapters of Acts. All others were lost. That is also true of our generation: those who believe are saved; those whose refusal to believe is a fixed decision are lost forever.