I've been burned out on Warband for some time now but when I try to play Bannerlord multiplayer I always feel I could be playing Warband instead and have a better time lol. Can't say anything about the singleplayer though. As weird as it is I have like 2100 hours in Warband multiplayer but never touched the singleplayer - will probably finally try it soon but I don't plan on playing Bannerlord's SP before that.
Edit: And yes, obviously it's still in Early Access but idk... I'm kind of sceptical of the final product as well rn. My current prediction is that it will take at least one year, maybe two, for it to really start replacing Warband but who knows for sure.