I don't think a lot of people would actually play a bg game for a whole year straight, there's just not that much to do beside the story, unless they want to replay it, but its only for the most dedicated. I'll probably finish my playthrough in a week or so, with all of the side quests done, and jump in to the starfield on release
The thing is you can only see one permutation of the story in one playthrough but there are a lot of permutations...and one playthrough is likely to be over 200 hours. So yeah, I can easily see this game lasting over a year. I'd imagine the minimum number of playthroughs for BG3 to be at least five before moving on from the game. But that's absolute minimum, realistically this will be a 10+ playthrough game.
Its not going to be a different story thought. You can play forever if you want to see every possible dialogue option, but I'm not really interested in creating the character, that I'm not associating with, only to see the different outcome in the same narrative that I've already experienced, and can pretty much already see what would happened. There could be some unexpected ways the story can go depending on that, but it usually not that drastic, and everything else would just feel repetitive. The main point of making choices is to set the tone of the story to your liking, and roleplay, not to grind endings. Its like reading a mystery gamebook but already know who the killer is. And you also have the possibility to side with the killer at some point, but why would you do that, if you want him in prison. Some people I guess would like to see every single sentence possible, but as I said, its for the most dedicated
