According to the data as of 9am this morning, Baldurs Gate 3 has sold 63% (since 6pm last night) of the total number of sales that Baldurs Gate 2 achieved in its release year. So I dont think theres any danger that it will globally kill the BG franchise, in terms of financial success its going to far outstrip any previous Baldurs Gate title.
I prefer turn based over RTWP - for much the same reasons as Chroniclard (I end up pausing so much that you might as well just give me a proper turn based mode), indeed the only reason I fell in love with Pathfinder Kingmaker was the turn based option. Having said that, I would prefer it if BG3 had both options, so that people could pick the one they prefer. Equally, having said that that, I would also prefer if every RTWP game ALSO had both options so that people could pick the one they prefer.
I've done 6 hours on BG3 so far and got to say I'm loving it. Looks great, looks more modern than many RTWP only games, enjoying the voice overs, liking the puzzles, enjoying the story and the combat, feels much more like I am playing D&D than most RTWP games that I have played and actually feels sufficiently different (aesthetics aside) from Divinity games that it feels like something new. The CRPG genre isnt one which is overflowing with new games, so I'm happy to just get one to play !