I
I am not saying make BG3 MMO... in saying is make a new game taking existing assets and engine and obviously work on it.
Of course I would expect at least 3-4 years on work for such a thing.
But that'd be better than starting from scratch with 0 assets and everything.
They'd have terrain assets, particle effects, spells, characters, etc etc already
I don't really think that works, either. Even assuming they wanted to, and that your 3~4 year estimate is correct (I expect would be closer to double those estimates), 4 years from now, most of us will still be playing BG3 and still finding new things, because it's freaking huge. Are they going to suddenly drop a new product that to a fair degree will be a direct competitor to a product new players will still be buying?
Either they go the DLC route, or start something entirely unrelated