There's no reason they can't use a different name. Divine Divinity 2 is the currently intended name for the game after Beyond Divinity because Beyond Divinity doesn't continue the story of Divine Divinity. It's just in the same universe.
Also, Divine Divinity 2 will have MMORPG support, I believe. (Or is it just multiplayer?)
I seriously doubt they will name it Divine Divinity 2. I'm convinced they will drop the Divine from the name.
And it's multiplayer support.
