We haven't changed the API, so everything should still work. For example, I just installed 4.1 versions of dashboard and support-plugin in master, and all's well [*]:
api.addSubTab('Template', 'Red Hat Documentation', 'my-host-subtab-template', '<url snip>', {alignRight: true});
api.setTabAccessible('my-host-subtab-template', true);
[*] however, note that "alignRight" is now ignored
And dashboard 4.1.8 installed in master engine:
That said, we probably should have sent some announcement about making sure the plugins actually look good with the new theme. If some plugins are greenish, that will look bad.
To help with styling external things, we've started exposing more CSS via a new SASS brand module: