Starting from recent appcompat library versions (I'm not sure which one exactly), the need to cast the result of findViewById seem to have gone away. In fact, if the casting in current form stays, then compiling with "-Xlint:unchecked" will raise warnings like this:

  required: T
  found:    View
  where T is a type-variable:
    T extends View declared in method <T>internalFindViewById(int)
/git/project/app/src/main/java/SomeActivity_.java:40: warning: [unchecked] unchecked cast
        return ((T) this.findViewById(id));

AndroidAnnotations version: 4.4.0
Android compile SDK version: 26

Annotated code:

@EActivity
public class SomeActivity extends AppCompatActivity {
}

Expected generated code:

@Override
public<T extends View> T internalFindViewById(int id) {
    return this.findViewById(id);
}

Actual generated code:

@Override
public<T extends View> T internalFindViewById(int id) {
    return ((T) this.findViewById(id));
}

This would probably require different style of code generation depending on the activities parent class (AppCompatActivity, Activity) and if the findViewById call supports the casting already.