Beamdog Software have confirmed that they are working on a new Baldur’s Gate game, but it isn’t Baldur’s Gate 3.
Instead, the game will be an interquel, connection together the story from Baldur’s Gate: Enhanced Edition and Baldur’s Gate II: Enhanced Edition. Like both these games, it will be using the new Infinity engine.
Beamdog also promises that this release will be bigger than any they have done before. We should get more details by this Spring, which would not be a bad time to release the game itself.