As confirmed by @BeltFanDan, new WWE Tag Team belts have been designed and are in New York for WrestleMania 35.
Whether they will debut during WrestleMania is uncertain at this time.
This could mean that the WWE are going forward with unifying a lot of the brand specific belts and there will be one set of tag belts that’ll be shared across RAW and SmackDown.
Either that, or each brand will have their own set with this new design.
Hopefully, we learn more, or even see these belts at WrestleMania this Sunday.