Have they? Are you sure you have seen Q1 2016 figures? The announcement to stop publicly releasing subscription figures, because people were reading too much in to them, was talked about on this forum for about 6 months straight. I don't think we have current subs figures to debate.
The interesting stat to me, is that WoD sold more copies than MoP or Cata. That tells me there is still a base that wants to play Wow, if Blizzard can deliver what they are looking for.