Merb + Rails merger

Update(2009.2.8)
"Merb in Action" => "Rails3 in Action"
http://www.manning.com/katz/

Table of Contents
1. Building Your First Rails 3.0 Application
2. Overview of the Rails stack(s) + architecture
3. Creating Rails Applications
4. Using DataMapper for Models
5. Using ActiveRecord for Models
6. Other Choices for Models
7. Processing Requests
8. Routing in Rails 3
9. Customizing Views
10. Working on the Client Side
11. Supporting Characters
12. Using the Plugin API
13. Testing Your Applications
14. Deploying a Rails Application
15. Scaling Rails

Appendix A Just enough advanced Ruby
Appendix B The migration story
Appendix C Rails 2 to Rails 3
Appendix D Merb 1 to Rails 3

Update(2009.2.5)
Rails 3 will have mountable applications, not engines or slices.

Update(2009.1.16)
I just got an email from manning about "Merb in Action".

• Rails becomes more modular, by building on rails-core with the ability to opt in or out of specific components and making it possible to replace parts of Rails without disturbing other parts.
• Merb performance improvements flow into Rails, including benchmarking applications so developers can see which optimizations have real-world impact.
• A defined public API with a test suite, so users and plugin developers have a stable API to build against.
• A "core" version of Rails, like Merb's current core generator, that makes it easy to select just the parts that are important for your app.
• DataMapper and Sequel support as first-class ORMs, along with ActiveRecord as the default.
• Rack support in Rails 3, to improve the state of modular, sharable logic between applications.

Update(2008/12/26)
So far, it seems that merb google group is the best source. And Matt Aimonetti answers all the concerns.

Yehuda Katz says
"If you want to learn Merb for modularity and power that is not currently present in Rails, stick with Merb. We'll provide a good upgrade path to Rails3 (and feel free to contact me personally to keep me honest on that promise), and you'll have a leg-up when the same power makes its way into Rails. While Rails3 will still be very similar to Rails2 for current Rails users, it will look a lot like Merb for those users who are currently drawn to Merb."

"We always said that there would be breaking changes in Merb 2.0. Now, some of those breaking changes will be in tandem with the Rails3 merger. However, we will treat them like any other breaking changes, and make sure the deprecation notices flow freely and the transition path is clean. Make sense?"

Matt Aimonetti says,
"The great advantage of using merb now, is that it has a public API so we will be able to easily migrate it to the new 3.0 API. Concretely, we are planning on being able to replace merb-core by rails-core in your merb app and to use merb-helpers and other plugins with rails-core."

I think "Merb in Action" would take longer than expected. And it's required to rewrite the whole chapters that are published. Of course, book's title will not be changed but I'm just worried about Merb. It would be called Rails3.0 by many other people, especially inside Rails community.

As Ezra said,

Merb is dead, long live Merb(Rails-3.0)!

Matt Aimonetti said,

I don't think Ezra is right. Merb isn't dead. First off, merb will still be around until the next release (rails 3.0) and we will keep on supporting it even after that (maintenance).

So many merbists are disappointed by this news but there is nothing can be done. Engin Yard's decision looks solid. I've accepted it, after all. I've read many articles enough to say that I will stick with Merb. There were some people who even want to switch to Django. I decided to practice Merb more than before. Because Merb would be the core changes in Rails3. And it could happen that Merb core team is too busy. But evangelist like Matt Aimonetti will help us. I hope taking this path would be natural to Merb2.