The first plan is the hardest and least accurate part of release planning. Fortunately you only have to do it once.
So now you know what a release plan looks like and how you use it. It should be clear that the accuracy of the plan depends on the accuracy of its estimates, and the accuracy of the estimates depends on the history of the project. The first plan has no history, so your estimates are flaky. What does this make the first plan?
Flaky. (Think Kramer with too much coffee.)
But you still need a plan to even get started. The plan gives you something to track against so you can assess progress. It gives you a framework of stories that allow you to notice what happens and build up the history to ...