THe thing is, you just can’t know what you are going to want in ten years, or what he is going to want, or anything. You (and he) can’t commit to never changing your mind about things. You both just have to plunge in and see what happens:
You could grow old together, neither of you ever wanting children.
You could break up over something completely different.
You could decide you want children in the future, he still doesn’t, you decide you want him more and stay with him.
You could decide you want children in the future, he still doesn’t, you decide you want children more and leave him.
You could decide you want children in the future, he still doesn’t, but he decides he is willing to have kids to keep you.
It could go the other way, with his mindset changing and you staying adamently committed to the child-free life, and again, either he’d leave, or he wouldn’t, or you’d have kids.
You could both decide you want children, and have a passel.
You could both decide you want children, and then discover you are unable to, adn readjust back to appriciating the advantages of a childfree life.
You just can’t predict it. All either of you can do is be honest about how you feel now. If in ten years, you decide you want kids more than you want him and you leave, that’s ok. You have that right. Just don’t promise not to change how you feel–or let him promise not to change-- because you don’t want to have the fight in ten years where you (or he) is yelling “This wasn’t the deal! You promised not to feel this way! You promised not to change!” You can’t promise that. You can’t ever be sure. You just make the best decision you can with the information you have and then reevaluate it when new information comes to light.