Bg4? LET TACTICAL ADVENTURE DO THAT. 🤔🤔🤔
They stated that they want to keep the studio small, so they are unlikely to be in position to ever be able to handle an IP of that scale. And while they implemented combat very well, I don't think they showed skill nor interested in areas I would consider key to great BG game - story, interesting characters, quest design.
As to OP - I don't believe Larian will want to continue working for WotC in the long run. Developing their own IPs is in the long run the best thing they can do.
Working on BG3 is an opportunity to raise the status of the studio and expand their audience, as well as expand their toolset while working on a high profile IP. I would be shocked if they weren't looking to use the enhancements that they have made to enrich the IP that their own. Having a strong IP raises studio's worth - making a great game for someone else, not so much.
While BG3 will most likely be very succesful, it will be a success shared between Larian and WotC - both financially and reputation wise. After all, Baldur's Gate and D&D isn't an IP that Larian can freely use in the future - not all will be so immersed to know who made BG3. Back in a day Bioware ended up going its own way, rather then working for Interplay/D&D owners, and I suspect Larian will do the same. They have showed that they are more interested in developing their own ideas rather then serving the IP. The goal is not to make best D&D game they can - it's to hook D&D/BG audience on D:OS formula through marriage of both.