It will likely come to the non pro here in a couple of years at most.
The iPads that have thunderbolt and usb3 use a separate physical usb controller for those speeds. The iPhone doesn’t have the space for that so they handle on the chip itself.
The non pro 15 is using the A16 from last year’s pro model that only supports usb 2. The pro this year has the A17 pro chip that supports it.
I suspect that next year when we get the rumored “ultra” iPhone, it will have an even beefier A18 Pro chip that will support thunderbolt 4 like the iPad Pro does with 40 gig, and the non pro iPhone will get the A17 which will handle base usb3 speed like the iPad Air does.