If the supplier has not declared their intent to bid, then no, they will not get the updated message. This is intentional because we want to avoid spamming a supplier that is not interested in an event they were invited to. You can send a seperate message to them letting them know. If you do that, make sure you are sending to them specifically, not just broadcast to "All Suppliers". The latter won't get sent to suppliers who have not declared interest to participate. You can select all participants by checking each of them then sending the message and it will get to them.
David