Peter says there are false prophets who arose among the people. I do not think Peter is prophesying of something new here. It is likely that he is speaking of the false teachers spoken of by Messiah (Matt. 7:15-23).
In this chapter in Matthew, we have a discourse by the Yeshua that speaks of the signs that point to His second coming and of the end of the age. The disciples already were familiar with what would happen on the last days because of the writings of the prophets (Zeph. 1:14-18, Micah 5:5-15, and many others). They knew it would be a terrible and dreadful time. They just didn’t know “when” it would take place. There are many out there who would love to set precise times and dates for the return of the Messiah, but He told us we would not know the hour or the day (Matt. 25:13).
This is another one of the classic misinterpreted passages in Scripture. People take this one phrase and use it without the ensuing passages following it. If we look at the entire passage, the message is clearly that we are not to judge others if we too are involved in that same sin, even to a worse degree.