To some, Rails is getting big. It brings a lot of functionality to the table. This makes apps easier to get off the ground, especially if you aren’t an expert. But, as apps grow, it can lead to the pain; there’s so much machinery in Rails, it’s likely you’re abusing something. It’s easy to look at other, smaller tools and think there’s green grass over there.
Rails 4 might have answers to this temptation.
On the controller side of things, it seems likely that some form of Strobe’s Rails extensions will find their way into Rails, making it easier to create apps (or sub-apps) that are focused on providing an API and eschew the parts of ActionPack that aren’t necessary for services. The thing I like a lot about this idea is it covers a gap between Sinatra and Rails. You can prototype your app with all the conveniences of Rails and then strip out the parts you don’t need as you grow the app and strip it down to provide quick services. You could certainly still rewrite services in Sinatra, Grape, or Goliath, but it’s nice to have an option.
On the model side of things, people are, well, modeling. Simpler ways to use use ActiveModel with ActionPack in Rails will appear in Rails 4. The components the DataMapper team is working on, in the form of Virtus seem really interesting too. If you want to get started now, you can check out ActiveAttr right now, sort of the bonus track version of ActiveModel. Chris Griego’s put a lot of solid thought into this; you definitely want to check out his slides on models everywhere; they’re lurking in your controllers, your requests, your responses, your API clients, everywhere.
In short, my best guess on Rails 4, right now, is that it will continue to give developers a curated set of choices and frameworks to get their application off the ground. It will add options to grow your application’s codebase sensably once it’s proven out.
What I know, for sure, is that the notion of Rails 4 seems really strange to me. How fast time flies. Uphill, both ways.