While it might not translate into # of subscriptions, I think it's good evidence that numbers are rising, especially over a time period.
Actually, hours played is much more interesting for me as a player, because it almost translates into activity and players online. Subscription numbers are the business side of it. There could be more subscribers (great for HTC) but still less players online (bad for the customer)
That being said, numbers went up with the release, followed by an immediate even larger drop. In the past 2 months the numbers seem to have stabilised, possibly even climbing a tiny bit. But still less than before the release of the new version. But then, after the release of AH2 there was a much larger drop in numbers and it took AH a long time to get back to pre release levels.