All of a sudden, all OnePlus 5 models are no longer available for purchase. This could mean two things - either there are problems and OnePlus is struggling with the availability or a new model is in the works. If you ask us, then we would say a new model is coming.
If we remember OnePlus 3, its successor was launched just five months later, in November. And since October has started, it is possible that either OnePlus 5T or OnePlus 6 will be announced any moment now. Unfortunately, we have no other information at the moment.