I don't think it'll come fo Fenix 5X. Actually BLE/ANT+ chip supports some level of NFC but I think just acts as a receiver and don't know how actually NFC and payment system works. Also NFC tags have some long copper coil antennas and Fenix 5X don't have them...
Please post a Link to a BLE/ANT chip that supports NFC...they don?t. Also antennae can be small but the larger they are the better the range is. Anyway, bottom line it?s a good guess the F5 doesn?t have the hardware in as I can?t see Garmin adding cost into the BOM without using it on launch. If someone has a tear down then it would be easy to work out.
NFC?-A tag support is included on chip. NFC Type 2 and Type 4 tag emulation protocol stacks are provided by Nordic opening up a range of new applications, like NFC payment, and improved user experience for existing BLE applications with Out-of-Band (OOB) pairing. OOB pairing using NFC simplifies the process of authenticated pairing between two Bluetooth devices by exchanging authentication information over an NFC link
don't know if newer protocol stacks are hardware independent and could be rolled out to other NFC devices.
some link about the partnership of Garmin and Nordic Semiconductor:
Good find, I was unaware of that. It's only tag emulation, so that wouldn't be good enough for the Garmin pay type of payment. Just done a bit of reading and for mobile payment you need an NFC controller, compliant with loads of standards eg EMV (https://www.emvco.com/) and there isn't a solution I could find with it integrated into a BLE SOC. The new Fitbit uses an NXP device (see https://www.dcrainmaker.com/2017/08/fitbit-ionic-gps-smartwatch-all-the-details.html for a tear-down). I'm guessing the Vivosmart 3 uses something similar.
Among the exhibits is a demonstration of how Nordic?s nRF52 Series Systems-on-Chip (SoCs) are increasingly being used at the heart of wearable contactless payment technology. The demonstration shows a Bluetooth low energy wearable using the nRF52832 SoC?s Near Field Communication (NFC) interface for payment.
i think they did implement GArmin Pay with and on top of the S332 SoftDevice v4.0.2 API or something similar. So at least it could have a major impact on older firmwares.