“Every sin and blasphemy will be forgiven, but blasphemy
against the Spirit will not.…either in this age or in the age to
come (Mt. 12:31-32; Mk. 3:29-30). This is saying that every sin
and blasphemy will be forgiven in the age to come except this sin.
If not, what is the point of singling out one sin in particular as an
exception? This is powerful testimony from the lips of Christ
Himself for hope after death! Because a particular sin will not be
forgiven at a given time does not require that the penalty be infinite.
Also, God‘s justice in judgment does not change! (Mal. 3:6).
All judgment is measured and with a purpose. Either a just penalty
will be exacted (He. 2:2), or its forgiveness must await a subsequent
age. (Scripture alludes to ―ages to come- Ep. 2:7). We can
rest assured that the Father‘s chastising penalty for this sin will be
just, and righteous, and in character with His loving heart for all.”
Assuming the dead are not conscious & the age to come is a period of 1000 years commencing at Christ’s future return, those who committed this sin, if any, after dying would sleep through that future age (the millennium) & be resurrected at the GWT judgement spoken of in Revelation. From that point on they could be pardoned of this sin.