Is it true that Allah Almighty will not forgive the killers of Husayn due to their heinous crime against the Prophetic Household?

"Al-Husayn ibn Ali (may Allah be pleased with him) was killed during the reign of Yazid ibn Mu'awiyah. This was one of the grave abominations committed by Yazid. He was killed by the aides of Yazid's governor, 'Ubayd Allah ibn Ziyad. The killing of a Muslim is a tremendous crime and a grave sin. Allah the Almighty said: 'But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allah has become angry with him and has cursed him and has prepared for him a great punishment' (Quran 4:93). A believer remains righteous as long as he has not shed forbidden blood. 'The perishing of the world is less significant to Allah than the unjust killing of a believer.' The correct view is that the killer of Al-Husayn falls under the general meaning of Allah's saying: 'Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills' (Quran 4:48)."