It's not going to happen. It can't.I'm a little surprised that they haven't already. It seems like such a natural fit for the cycling crowd. I know you can sync bluetooth accessories, but ANY+ is a pretty glaring omission.
Garmin owns the Ant+ protocol and ended certification officially last June. Bluetooth BLE is the immediate future (or rather present).
The writing was on the wall before the Apple Watch even launched due to the EU in 2014 adopting the Directive 2014/53/EU Radio Equipment Directive (RED).
Ant+ doesn't have encryption, which Apple would've been against to begin with, but that was the driving force behind the directive. It also simplifies components since Bluetooth was going to be needed anyway.
I just upgraded all of my bike tech and it's all Bluetooth. There's a lot of gym equipment that will take a long time to switch over, but no new equipment is going to be Ant+.