Same happened to me last Friday with Emirates to London via Dubai. Was downgraded from Business to Economy (technical issue in 1st Class) on the first leg to Dubai AND missed connecting flight, when we landed in Dubai all paperwork was ready and was whisked by chauffeur to a 5* hotel and room for 12 hours, free meals etc in any of the hotel restaurants.
I had only booked a ONE WAY flight to UK in Business Class, so was disappointing the 1st leg was downgraded to economy BUT as compensation, they gave me a RETURN Business Class Flight from Bangkok to London to use in next 12 months!