protected_attributes

It does not, you can actually pull in a gem[1] to use attr_accessible just fine with Rails 4. If you want to transition to strong_parameters, you can include the gem in your Rails 3 project and begin migrating to it, though that's a tough sell on most Rails codebases I've seen as it requires you to update every action in your app. I have not personally migrated any of my code to Rails 4 from 3.2 yet but the transition will be far smoother than 2.3->3 was. [1] - https://github.com/rails/protected_attributes

It's a way smoother upgrade - exactly as you mentioned really the only major change is from attr_accessible to strong parameters however you can still include the protected attributes gem for a quicker/easier upgrade path (https://github.com/rails/protected_attributes)

3.2 -> 4 is an order of magnitude easier than 2 -> 3. The upgrade guide is pretty solid, and I imagine it mostly applies for Rails 4.1 as well: http://guides.rubyonrails.org/upgrading_ruby_on_rails.html#u... I spent most of my time updating app config. For several of my 3.2 apps, I started using strong_parameters, so it wasn't a leap for me. Another app I have on 4.0 is using the https://github.com/rails/protected_attributes to retain the existing attr_accessible behavior until I get time to update. Hope that helps!

I'm not 100% sure, but I believe you can upgrade without a lot of rewriting by using the protected_attributes gem (https://github.com/rails/protected_attributes).