Before You Communicate
As a project manager, you first need to analyze the received information in order to determine if there are immediate alternatives. Processing alternatives will allow you to understand how to mitigate any damages or losses from the unknown change. You can create alternative plans based on worse and best case scenarios. Understand that just listening to one side of a situation is never a good practice. As you create your best and worse case scenarios, think that the individual or group telling you about the uncertain change may have placed their best interests before the actual project. This should help you better understand how to create effective alternatives.
You need to ask questions to determine a resolution. In the above scenario, you only know one thing, that the project will be delayed. When you only know about a change, and there are no other identified barriers or end-results, then you have to ask questions. Asking questions can help you find resolutions on how to plan and finalize other processes for the project. Oftentimes, asking questions can help you immediately identify an alternative solution. Asking questions also help with identifying any resolvable issues. In the scenario above, if you take the time to ask a few important questions, then you may be able to find out where the delay originated from. Questions also help you identify and create a new communication strategy regardless if you are still uncertain of when a change will become effective.
Once you have analyzed the necessary information and asked the important questions, you should begin working on a new plan of communication. Your communication plan should detail the project, the changes and your estimated time for implementation. Again, if you are uncertain of the change effective date, do not worry because you will still have a plan to implement. If you are working with a team, then you also need to communicate the change with them.