ApplePay is coming to the TTC.
In London, UK Apple Pay is already accepted. You tap on, then tap off and the TfL system recognizes it. This only works in cooperation with Apple since each ApplePay tap generates a random credit card number and wouldn't be recognized as the same card tapping out. There are also weekly maximums if you use the same ApplePay card when you commute. The TTC will work the same way.
For the TTC this refers to purchasing fares. In fact they already support it at the Presto Self-Serve Reload Kiosks and at collector booths for purchases over $10 (I believe they take tap?), as well as at the LFLRV onboard/offboard fare machines for cash fare purchases. And as I've mentioned elsewhere, Apple Pay is in fact no different, in terms of "supporting" it, than tap-to-pay Visa/Interac/etc. If you can tap debit or credit, congratulations, that merchant accepts Apple Pay.
The only "coming soon" Apple Pay/Credit/Debit support on the TTC is at collector booths for single cash fares/purchases under $10. To be clear this does not mean TfL-style support as a presto replacement.
Also, Apple Pay doesn't actually generate a unique
card number for each transaction--it generates a unique
device account number for the combination of device+card, i.e. my Phone has one for my Visa and one for my Debit, my Watch has a different one for my Visa and for my Debit. That number is unique to the device+card, but does not change between transactions--this is how TfL works, and if you ever need to return something at a store in person it's how that's possible.
On Android, it's more straightforward. PRESTO can release an app that uses any Android's NFC chip which is open to developers.
As I've said multiple times in the recent pages of this thread, Apple is in the process of rolling out support for third-party NFC cards through Apple Pay, which would include Presto if Metrolinx ever cares to add support for it. Full support should be available on Apple's end no later than September/October this year with the release of iOS 10. Yes, Android has supported it for years--in fact on an old Android phone I had, if you tapped the presto card to the phone it made a beep but did nothing else--but Metrolinx is lagging behind here...Android users could have had it probably in 2011-2012.