Sprint is on its way to oblivion now that the T-Mobile merger has received government approval, but the increasingly troubled carrier is still going through the motions. It is even preparing to launch a new 5G device with OnePlus. However, Sprint has chosen to keep practically all the details to themselves.
As you may know, OnePlus launched a 5G version of OnePlus 7 Pro in select markets. The United States was not one of those markets because we do not have much midrange 5G, which is what OnePlus supported. Now that Sprint has launched its 5G network in the 2.5 GHz band, we have some mid-band 5G. It is not inconceivable that OnePlus could get a version of 7 Pro on Sprint in the near future.
Sprint says it will announce specifications, pricing and launch timing "soon." The mystery phone will get 5G services in areas of Atlanta, Chicago, Dallas-Fort Worth, Houston and Kansas City. Sprint's 5G coverage is more expansive than other carriers due to lower frequency. It is unclear whether you will be able to get the 5G OnePlus phone in other markets.