To avoid confusion, note that 'subscriber' has always included anybody who logs into WoW from a net cafe once every 30 days, which is how a lot of asian players access the game. This is where a lot of the volatility has come from ever since Wrath came out.
Q2 2012: 9 million
Q3 2012: 10 million
Q4 2012: 9.6 million
today: 8.3 million
This represents a 5-year low for WoW's numbers. I guess Titan can't come soon enough for Blizzard. Even if we see another WoW expansion it's likely the sub base will contract to Vanilla levels by this time next year.