I find the idea of a genre getting bad when introduced to the mainstream to carry a degree of arrogance to it. Game of Thrones was firmly mainstream and everyone liked it for its darkness and complexity and violence, and turned on the genre hard when that went away. I think people's idea of main stream is just a little too unkind for the most part. Im sure we'll probably see some crpgs come out geared to a more casual crowd, but I don't believe that equates to a loss of hard-core products. I even think that the hard-core audience will end up seeing a net growth (though probably not a huge one, in all likelihood) since inevitably there will be a percentage of people who want more of this kind of game and will branch out, with his as their introduction.

As for worries about games trying to include more sex for marketing, games have been doing that more and more for decades. Look at Dragon Age and Mass Effect. If its gonna be a problem, it's not BG3s fault.