Anytime a sale is subject to probate approval, it means that it will take longer than normal to close.
The average estate can take six to nine months to go through the entire probate process. More complex estates can take up to one year to complete the process. Each situation is unique and it depends on where this estate is in the process.
If you are working with a Realtor, then they should be able to get you an estimate from the listing agent as to when they expect to receive the approval from probate. This is a conversation you should have with your agent or broker.