I personally look forward to this new development and always strive for developers to make the game they want and what inspires them instead of what other people urges them to do(especially not the cheepskates on here who don't pay for nothing). So I just wanna say I support you and there are plenty of people who like swinging or don't mind it, if it is optional
That said, I must advice you to not state there will be no NTR if you aren't sure you won't add it. Its better to not make statements like this unless you are absolutely certain. In fact, I encourage you not even reply to questions like this because I know game development takes time and most devs don't have the whole game and its kinks/fetishes figured out from the beginning.
I know its tempting to tell people what they want to hear, but remember; nobody here has any right to demand you promise them anything. So its better not even respond to people asking if there will be NTR or not.
That way, you are not locking yourself to a path you might not want to follow and you prevent
all the rage if you do decide to add it. Sure some people will complain, but as long as you did not state there will not be NTR, they have no fair argument and their posts will be swiftly dealt with and removed if they shit on you for it.
Just my two cents. I'm very optimistic about this game and you can be sure there is a fanbase for the kinks your enjoy too. The fans who leaves the game now will easily be replaced by those who enjoy swinging and those who don't mind it will stay. Don't loose hope