I'm not aware of any such plans now (I assume by support, you mean an ability to switch between themes in the UI?).
1320: theme: 'eclipse',
17: *= require codemirror/theme/eclipse
If the theme you'd like to use already lives in
vendor/assets/bower_components/codemirror/theme/, switching the theme should really be as easy as changing those 2 strings .
Hope it helps!