fortune_p_dawg: they could almost just call it Divinity Original Sin 3 (or even 2.5).
I got this from the gameplay video as well. Basically, DivOS 3 with D&D rules and setting. I don't actually think there is anything magical about the D&D setting or rules (and I would probably cringe at any BG1&2 chars appearing in the new game), so I think I'd prefer if they just dropped it. It places third party restrictions on what they want to do (one such situation was even brought up during the demo). Calling it BG3 also makes people expect BG1-2 things. Given that different people have different reasons for liking BG1-2, it's impossible to satisfy all of them. For example, I love BG1-2, but I heavily disagree with the analysis video posted by Breja earlier.
On the other hand, the demo was awesome, in spite of bugs and bad luck. So, even though this game is pretty much guaranteed to lack Linux support, I will get it as soon as the price is low enough to compensate for the risk of not even working on wine.
For people who want a more BG-like game, the new Pathfinder game will likely be awesome as well (and probably Linux native), so there are at least two epic RPGs coming soon.