People often ask questions like "What is the difference between Scrum/XP/Lean/Agile/You name it"? I don't see much difference between XP and Scrum on that matter. If you already have XP, most likely don't need to switch. Maybe adopt some Scrum specific practices for a better scalability like Scrum-of-Scrums. Almost all the other practices like daily meetings, iterations, roles separation, retrospectives, etc. exist in XP already.
In fact I am not sure if such separation brings benefits. It is better to spot what's going wrong in your development process during retrospective meetings and apply practices from any agile process (or create own solutions) to your specific problems. XP, Scrum or Lean give you a framework that helps to be adaptive and creative, whereas traditional processes give you a set of rules hindering any creative behavior.
Your team and your project IS special. Think and communicate to sharpen your development process.
I do understand why people are so enthusiastic about Scrum or XP. These processes provide tools and practices out of the box. You may just start doing it and see what happens. It is not the best way, since quite often agile adoption fails. People don't get the new way, they implement it without proper support and under the pressure. They maybe don't have a deep understanding how it should work. So it is expected that agile adoption might not be smooth for all.
Agile Development Future
I wish all agile methodologies evolve into one elegant, smart, simple framework. For me it is a natural trend and it should be something like Theory of Everything in physics. This framework should explain why agile processes work. It should based on natural laws of Complex Adaptive Systems. It should provide general guidance on agile adoption and a repository of possible practices that might be used to build your own development process. The framework should be simple and unobtrusive, since complex rules will not work for software development. The framework should empower creativity, communication, learning, feedback and self-organization. The framework should support nonlinearity, emergence and edge of chaos concepts.
Software development is young. Currently we are having transition from waterfall to agile. It is mainly based on practice rather than theory. Practice has proven that agile works better. However, there's almost no research explaining why. There are some blog posts and short explanations with reference to Complexity Theory. That is a right direction I think, but there's no depth behind these posts, they are quite superficial.
I expect we will have deeper understanding of the agile roots and why it works. This knowledge will simplify transition and help us to find better practices, patterns and solutions. I expect there will be a unified agile software development framework in the future.
So far Scrum and Lean are closest processes to this framework. Lean has a strong philosophy and nice background. It is general enough. Scrum is simpler and more understandable for mere mortals. XP has a set of best practices and heavier in general. All of them have strong and weak sides. But still I feel there's a deeper level and all modern processes are just a subset of some hypothetical (at the moment) unified agile software development framework.