Re the KJV original, consider this sentence I am writing as an example of the usage: A mother sees her kids playing ball inside and says, "I will not have this nonsense in my house!" That is the sense in which Jesus is saying "I will have mercy..." He is not merely stating what will happen in the indeterminate future by indeterminate persons, he is issuing a command to his followers. In this way the New Living translation makes the meaning clear who is to do what, and that they will do it because he said to do it. It will not occur by accident and he is not just foretelling its occurance in a crystal ball.
I actually can agree with that.