First, let's back up: Sprint’s 5G network is currently live in five US cities and is expected to imminently expand to LA, New York, Phoenix, and Washington, DC. And it has confirmed a 5G smartphone from OnePlus will become the fourth 5G device it carries, alongside the LG V50, Samsung Galaxy S10 5G, and HTC 5G Hub. But Sprint hasn't revealed which 5G device it's getting from OnePlus.
There are no details about a release date, pricing, or specifications. While one would presume it is getting the new OnePlus 7 Pro 5G, the media has been quick to note that OnePlus is expected to reveal a successor later this year. If you think that's a short life span, keep in mind OnePlus pushes out mid-cycle "T" devices. For instance, OnePlus 6T debuted about six months after the OnePlus 6.
Like clockwork, images recently appeared online showing what's said to be the OnePlus 7T Pro. Add it up, and it's likely the OnePlus 7T Pro is a 5G device headed to Sprint US. But none of that is official, so your guess is as good as ours.