QR27/28 slots are already in use ... they represent Qatar Airways' popular lunchtime service into MAN, one of upto three flights per day on DOH-MAN. Ops currently use B787-9 equipment since the change to Winter schedules, taking over from the B777-300ER's which operated during the Summer.
It would be a major surprise if QR27/28 slots went unused in S22. The real question is, what type will operate the service. If the issue which has grounded a number of QR A350's is resolved it could be those; I believe that these were the originally intended type for the route. But in their absence, the A380 could step up. Given that the PIA schedule to MAN remains very thin (relying on sub-leased A330-200 aircraft at low frequency) and that the Jet Airways Mumbai service has not been replaced, demand for connecting seats to the Indian Sub-Continent should underpin buoyant demand for reliable connecting services. And the capacity difference between an A350-1000 and an A380 isn't that great.