Can us menfolks change our minds? Sure. Should you expect it to happen? Not at all. If that man says he’s not getting married until he’s 30, then you should believe him. Marriage isn’t something you enter into all willy nilly. It’s not like deciding between wheat or whole grain bread. And it’s something he probably feels strongly about.
So no, you shouldn’t hope (or expect) that he’ll change his mind.
I tend to think that nearly everbody has something they won’t budge on. It varies from person to person but for many men, getting married before they’re ready to is one of those things. And if he’s saying 30, then you should expect that he means 30 and while I know that might annoy you and make you feel like if he loved you, he’d consider it, the truth is, he’s drawn his line in the sand. It’s your choice whether you cross it or not.
I’ll go a step further here too, if you intend to break up with him in hopes that he’ll recognize what he’s risking losing in order to force his hand, you’d better be prepared to lose him. I know myself, I suck with ultimatums. Almost on principle I’ll do the opposite of what you want. Especially if it’s on something I’ve made clear so there are no surprises, which is what seems to be the case here.
If he changes his mind, be pleasantly surprised, but don’t expect it to happen.