"For those, it is expected that Allah will pardon them." And "'asa" (it is expected) from Allah is binding (certain).
﴿فَأُولَئِكَ عَسَى اللَّهُ أَنْ يَعْفُوَ عَنْهُم﴾ و ﴿عَسى﴾ من الله وَاجِبَة.