According to Jeremiah 32 the king is asking him why he made that prophecy, and then states the prophecy.

"For Zedekiah king of Judah had shut him up, saying, Wherefore dost thou prophesy (in other words why are you saying this), and say, ......

So I don't think it needs to end with a question mark and I also don't believe that if the other editions disagree with that, that they are wrong.