K.E.
My son does not seem to like cow's milk, so I just continue to buy formula for him. He's 15 months old now, and I get all kinds of looks and comments about how he should be off formula by now, but I just kindly let them know that I do what works for us. It's basically just nice way to tell them to keep their mouths shut. ;D
I wouldn't worry about it, it I were you, and if you're fine buying formula, then do it. I think it's more about nutrition than anything else. He will have plenty of opportunities to try different food and drink. For now, give him what he likes.
K.