All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
This matter is a matter of the unseen that should only be based on religious texts from the Quran or the Sunnah of the Messenger . Allaah says (what means): {And in anything over which you disagree - its ruling is [to be referred] to Allaah. [Say:] That is Allaah, my Lord; upon Him I have relied, and to Him I turn back.} [Quran 42:10]
We have already stated some Islamic texts in regard to the fate of the parents of the Prophet in fataawa 1041 and 10467.
However, we are not aware of any evidence that confirms or denies that they will be eternally in Hellfire.
There is a prophetic hadeeth in regard to alleviating the punishment of Abu Taalib, the uncle of the Prophet but analogy (inference) in such matters is not acceptable.
A Muslim should not get involved in such matters; it is more appropriate for him to be preoccupied with matters that involve rewardable actions.
Allaah knows best.