Just like a baby will choose which signs they learn to sign based on their interests, a toddler will decide which signs they continue signing as their verbal language develops.
Every baby is different. Some babies will speak very early and very clearly and so signs will quickly take a backseat to spoken words. Other babies will take up talking at a slower rate and will rely more on signs to get them by. By in large, most babies will show a mix. However, it would be a mistake to think that signs prohibit spoken language development and this myth has been dispelled previously. What will happen with babies who talk later is that they will use signs to help get them by on the words they find difficult to say. Babies find making certain sounds easier than others.
My son, for example, had trouble saying certain sounds while others came easily. Trough trial and error, he corrected this. But he figured out which sounds he couldn’t make and would use signs to clarify what he meant. When we told him we didn’t know what he meant, he would do the sign to accompany his best attempt at a sign. Sometimes his signs were also approximated and so he’d have a verbal and sign approximation going at the same time. By coupling both of them, we figured out what he meant. As your child develops verbally, signs will be a great tool they can use to help convey their thoughts with more clarity. Once it’s clearly understood what is meant, the signs will be stripped away. That is unless your family continues to sign into toddler years. In this case, your child will simply fall in line with what’s normal for the house. Toddlers are excellent imitators and are easily let by example.