The trade mark filing could suggest a number of things. Firstly, it might mean the successor to the Oppo Find X might not be called the Find X2, as rumours have previously suggested, and instead opt for the Find Z.
The Find Z name could also refer to a completely new range of devices though. It is thought the company could reveal a foldable phone at Mobile World Congress 2019 so perhaps the Find Z will be the foldable device?
Oppo has confirmed it will reveal a new 10X optical zoom camera system at MWC, but it hasn't revealed which device, or devices, the 10X camera system will appear on. Some rumours have suggested the Find F19 and F19 Pro might be the first to offer the camera system but nothing is official yet.
The Oppo Find X2, or perhaps Find Z now, isn't expected until around June. It is likely we will find out more about Oppo's plans at the end of February, but for now, it sounds like another new smartphone is incoming under the Find Z name. It is just not yet clear what.