There is most probaly going to be a BG3 as I have said many times before. It is not certain and will not be about child of Bhaal saga of course but the developers at black isle have said they do want to make a BG3 and it will maybe be set in a city like Waterdeep.
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"I was born of darkness. My fathers eyes closed before mine opened. I am not of this world or the other, and I have the right to be what I am..."