One way to approach this question is to consider that all of the characters are left realizing that, although their behavior may have been influenced by the magical spell cast on them, they also must accept that they are responsible for their own behavior. Their adultery, cruelty, and lack of compassion were all voluntary actions, however they may have been uncharacteristic at the time, and there is a sense in the play that, despite the lifting of the magical effects of Puck's spell, these characters have been irrevocably changed by seeing what they are capable of and knowing they must ultimately bear responsibility for their actions.
Some of things that remain unresolved, in this play are:
Oberon does not get what he wanted, which was the boy that Titania is protecting (her squire).
Bottom is left with memories of what happened and this leaves him confused and distressed. The lasting effect that this will have is unknown.
Lysander and Demitrius are not aware of why their feelings changed. For Lysander this was remedied but Demitrius remains under the magical effects iof the flower and we wonder how long this will last? Will the effects wear off in time ?
Helena also doubted Demitrius' love for her and this must remain in her mind. She was under the impression that they were teasing her in the woods and somehow this must stay in her mind. What will the future bring for their relationship.