"And they will not beget except [with] wickedness and disbelief" means: if they were to beget a child, he would grow up to be a disbeliever. This is something Noah knew from Allah, which is His statement: "And it was revealed to Noah that no one will believe from your people except those who have already believed."
﴿وَلا يَلِدُوا إِلا فَاجِرًا كَفَّارًا﴾ أَيْ: أَنَّهُمْ إِنْ وَلَدُوا وَلِيدًا فأدْرك كفَرَ وَهُوَ شَيْءٌ عَلِمَهُ نُوحٌ مِنْ قِبَل اللَّهِ وَهُوَ قَوْلُهُ: ﴿وَأُوحِيَ إِلَى نُوحٍ أَنَّهُ لَنْ يُؤْمِنَ مِنْ قَوْمِكَ إِلا من قد آمن﴾
