Future Oppo (and OnePlus) smartphones may no longer require a magnetic case to work with its Oppo Mag line of accessories. However, the addition of true magnetic wireless charging may come at the expense of a smaller battery capacity.https://www.notebookcheck.net/Oppo-and-OnePlus-is-developing-true-magnetic-wireless-charging-for-its-smartphones.1042135.0.html
Oppo N5 already has wireless charging built in. They just don't sell it here in the US. I have it though (purchased overseas and using in US) and can tell you it has wireless charging built in, no case needed.