Your older child's (or children's) reactions to their new brother or sister, and where they sleep, can range from being uninterested, to feeling very emotionally threatened by the new baby. The arrival of a new brother or sister can sometimes also mean a change in sleeping arrangements for an older child.
Ideally, alterations in sleeping arrangements should be started at least a few months before the birth of new baby (but expect a regression in your progress once the baby arrives). However, allowing an adjustment time for the older child (or other children, if siblings now need to share bedrooms), can disassociate the changes from the actual arrival of the new baby (which will be an adjustment in itself).
The age of your older child (and where they were sleeping 'pre-baby') will have a bearing on the impact of any altered sleeping arrangements. Older siblings who already have their own room, may not react as much as a toddler who sleeps (all or part of their sleeping time) in their parent's bed, or in a separate bed in their parent's bedroom.
You may consider setting up a single bed, or mattress bedside your bed (if you have the room) for your older child. This may be the answer if you are concerned about their reaction, or you may simply prefer to have everyone together. Alternatively, you may feel it is time for your older child to 'move on', and the new baby is a good excuse to do this.
Whatever the situation, siblings will generally voice an opinion (or display a reaction) when it becomes apparent where the new baby is sleeping. Even when the older child really does not wish to share their bedroom, they can still feel left out, or jealous, if the baby is sleeping in their parent's bed, or in the same room. Explaining that the baby's crying may wake them at night may help them understand why you have made your decision.