I'm disappointed, not so much for the loss of BG4, but for the lack of any new DnD settings from Larian. Whether that be something in Cormyr or a new Dark Sun or some other setting.
I applaud the desire to do something new. Too often in life these days, we get rehashes of previous titles. Movies do this all the time and it reaches the point where you start to wonder where all the creativity went.
My concern is that a new ruleset could be a recipe for disaster. The ruleset itself holds equal importance to all the flavor of the setting. We all know DnD, and for all its flaws, it's packaged into something that works well enough to support the flavor of the story being told. A new system will have to be brilliant to compete, and that's a tall order.
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I do get the impression that WotC is the reason we're not getting another DnD title from Larian. With the right deal, I think things would have progressed smoothly, but I suspect that Hasbro overestimated the importance of their IP and underestimated the importance of Larian.
The stagnant corporate culture probably didn't make things any easier.