Apple recently registered six new product model numbers (A1977, A1978, A1975, A1976, A2007 and A2008) with the Eurasian Economic Commission (EEC), as spotted by French site Consomac.
According to a translation of the filing's text, the model numbers refer to "wearable electronic devices" that run WatchOS 5. The unreleased models are also listed next to old model numbers for previous Apple Watch versions, giving strong evidence that this is the Apple Watch Series 4.
The six new Apple Watch model numbers don't necessarily mean that Apple will release six new Apple Watches. Instead, it's likely that the different numbers refer to different configurations like LTE and non-LTE compatibility or materials used.