I've just updated from alpha37 to alpha38, and all my components are now seemingly rendered with the behaviour ViewEncapsulation.None. Manually setting a component's encapsulation to Emulated restores the previous behaviour.

Going through the ng2 source, there no longer seems to be any code to make Emulated the default. In particular, this line:

this.encapsulation = isPresent(encapsulation) ? encapsulation : ViewEncapsulation.Emulated;

formerly of core/render/api, in a block of code that seems to have been moved to core/metadata/view, is no longer present in the same block of code. While that might be a red herring, it does seem that all remaining references to ViewEncapsulation.Emulated are strict comparisons, without any faculty for it to be the fallback.