According to a tweet from Nokishita, Sony has registered a new camera body, labelled WW734234 with an overseas certification body. It’s equipped with 5Ghz/2.4Ghz WiFi and Bluetooth. It’s the second currently unreleased-but-registered body we know of, alongside WW356015 (which also has 2.4Ghz WiFi and Bluetooth).
They also confirmed that these aren’t the recently announced A7R IIIa and A7R IVa (which are basically the old A7R III and A7R IV but with a higher resolution LCD). The A7R IVa is WW447485/WW778752 and the A7R IIIa is WW186333. It’s been suggested that the new code could be the Sony A7 IV.