Towards the end of the preceding verse it was said that the punishment of the Hereafter is severe. How severe it will be is now the subject of the present verse.
The severity of the punishment against which the polytheists have been warned will unfold itself when their leaders whom they followed will disown them as their votaries; and they both, the leaders and the led, will witness the punishment, and whatever bonds of leading and following may have existed between them would be snapped apart, very much like it happens in our mortal world when people share in the illegal but wriggle out when apprehended, so much so, that they would even go to the limit of refusing to recognize their accomplices!
When the so-called 'people' of their leaders will see this turnabout of theirs, they will fret and fume but will be unable to do anything about it except wishing that there be a return for them to the mortal world where they could, at least, square up with their greasy leaders - 'May be this time they come back to us seeking our allegiance which would be a perfect time to say no to them and to distance ourselves from them and to do to them what they did to us.'
But, what price are these dreams now? They are not going anywhere. They are stuck with 'their deeds which they see as remorse', and they all, the leaders and their followers, 'are not to come out from the Fire', since the punishment for shirk, the grave sin of associating partners with Allah, is to remain in the Fire for ever.