Hi T.,
My little boy is 19 months, and he still gets 3 bottles per day. He will drink ANYTHING out of a sippy cup, but MILK. There will come a day when he will willing give up his bottle. Our goal is 2 for his bottle and 3 for his passy. My son is a very "comfort" driven little guy. For him, the bottle is a something that comforts him, and I'm ok with that. I don't think it will hurt his teeth. He drinks 6 to 7 ounces in about 5 minutes flat, so the bottle is in his mouth a very short amount of time. You may want to think of giving him his milk/formula a little earlier than his bedtime, then brush his teeth before he goes to bed. Maybe you could rock him to sleep instead of him falling asleep right after the bottle, or put water in the bottle instead. Protecting those teeth is the only thing I would suggest that you change with your routine!
Also, we still rock our son to sleep as well (and again, he is 19 months old). Within 5 to 10 minuites he's asleep. We lay him in his crib and he sleep for 10 to 10.5 hours. So comforting a baby to sleep (rocking, singing, laying with him) isn't necessarily setting him up for sleeping problems, as some people would suggest. That certainly isn't that way it happens at my house!!
I firmly believe that every child is different, and it's best to work off of what they are ready for within reason. Of course a 4 y/o with a bottle is not within reason. Doctor's are wonderful to give medical advise, but I think when it comes to parenting advice, they overstep their bounds too often!!