Im so ready. This boss fight looks amazing and the fact From chose to show it tells me theres even better stuff waiting for us. The electricity effects are absolutely amazing. This is most definitely from their latest build.
Longer than Demon's Souls, around the same length as Dark Souls IIRC, so I est. around 50-60 hrs depending on how you play through the game. Also the Chalice Dungeon adds a random-generated dungeon element for optional play as well.
They started work on this after the Artorias of the Abyss DLC/Prepare To Die PC Edition released for Dark Souls 1
1) The "total game volume" is greater than Demon's Souls. Souls games do not split single and multiplayer modes, though in BB there is also the Chalice Dungeon area which is optional and has its own special multiplayer elements (like sharing dungeon configurations with friends).
2) They've been working on it since they finished AOTA DLC for Dark Souls 1.