An infant who is used to sucking from a bottle may have difficulty sucking from a breast. Both the sucking techniques employed in fact are quite different. It is explained thus: The bottle receiving mouth technique consists of rounding the lips, expecting the food to come from straight in front, and holding the tongue high and close to the palate. It is as if the baby were guarding against having something thrust too far into his mouth, whereas the baby taking the breast needs to use a small indrawing action to pull the nipple into a widely opened mouth. Once the babys technique has been adjusted to taking a bottle, it becomes much harder to get him to take the breast, but competition from the bottle does not matter, the baby becomes skilled with both.
Thus, since you have been breastfeeding him regularly till now, the baby should have no problem adjusting to both.