Will Windows 10 Mobile have Wi-Fi calling and texting built into the OS?

[Windows Central Question]

I am on T-Mobile in the U.S., and I use Wi-Fi calling and texting a lot on my Lumia 925. I believe T-Mobile has specific firmware to enable this feature. I would like to upgrade to a 950 or 950XL, but if T-Mobile does not sell these phones, I would consider an unlocked 950, but I need the Wi-Fi Calling and texting feature. Can Windows 10 Mobile do Wi-Fi calling and texting without specific firmware from the carriers?