BT4 is almost done, but not production level. You should raise a ticket about it to bugzilla. That it was promised. The part missing from BT4 stack (the uncomplete part) is BT LE (Low Energy)... It's really interesting for lot of accessory cases, but those are still so new that ordinary user would not be benefitting from those much within a year or so. May be the reason why it hasn't been perfectly completed yet....