If you've attended any of my Product Owner workshops or many of my conference sessions, you know that I often talk about release planning as a necessary extension to any of the agile methods.
From my perspective, it almost doesn't matter if you're leveraging Extreme Programming, Scrum, Kanban or some variation. If you're working in a context where you need to communicate release plans and make some sort of commitment to your stakeholders, then I think you should be doing release planning.
Now clearly it's not a silver bullet and you sure can't guarantee fixed scope & date commitments. But it certainly helps your teams align what's feasible within your release train tempo.
Here's a link to an article / 3-part post series I've written on the topic. I hope you find some value in it.
Stay agile my friends,
Bob.