You have described the last lines in the play, so the prince is not going to say specifically who is going to be pardoned and who will be punished. However, it does seem as though he feels sorry for those involved.
Notice, however, that the prince has actually backed off his earlier stance. When he first reads the friar’s letter, he is very angry.
Where be these enemies? Capulet, Montage,
See what a scourge is laid upon your hate,
That heaven finds means to kill your joys with love!
And I, for winking at you, discords too,(305)
Have lost a brace of kinsmen. All are punish'd. (enotes pdf p. 115)
He does say all are punished. However, Capulet responds by asking for Montague’s hand and forgiving him, and then Montague forgives Capulet.
The prince is heartened by this. He responds:
A glooming peace this morning with it brings.
The sun for sorrow will not show his head.
Go hence, to have more talk of these sad things; (p. 115)
From this, it seems as if Montague and Capulet will not be punished. It also seems clear that he does not want to punish the friar. When he read the letter, he said:
This letter doth make good the friar's words, (p. 115)
What he is saying is that the friar’s story was confirmed. Romeo and Juliet’s deaths were a big mistake. The friar is not actually culpable. Of course, a few lines later he said “all are punish’d” and that is not clear to include the friar, but given that he has forgiven Montague and Capulet it is likely.