Glad you like your Plus -- that's what I'm getting (eventually. Sigh -- waited 30 minutes for the Apple store to come up and when it did I was already three weeks out of shipping). My wife is getting the 6 because she doesn't need/want the Phablet factor.
But I wouldn't hold out hope for iOS 9 supporting AptX. Let's face it, the technology has been around for over 20 years so there is no way Apple is "suddenly" going to implement it. It's proprietary, and Apple has a long history of not using other proprietary technology. The one and only way it will ever appear in iOS is if Apple buys CSR (which is certainly a possibility).
(And before folks start saying "well, it's in OS X" remember that that's a Unix based system which already has hooks for the technology. It's a whole different ballgame to adapt to a different OS. Since OS X is actually migrating to more of an iOS structure, it's more likely that support for AptX will disappear entirely from Apple rather than suddenly appear everywhere).