In the past, OnePlus hasn't typically given its phones an official IP water resistance rating, saying that the certification process isn't worth the cost. Last year we saw the OnePlus 8 Pro get an official IP rating, though, and it looks like next year's Pro model may get one, too.
The OnePlus 9 Pro will reportedly come with an official IP68 rating for dust and water resistance. That's according to leaker Max Jambor, who has a history of OnePlus leaks.
Today's leak says that the regular OnePlus 9 and the rumored OnePlus 9E will not get an official IP rating like their Pro sibling. That doesn't necessarily mean that they won't be water resistant, just that OnePlus might feel that the priciest Pro model is the only OnePlus 9 variant that warrants the added cost of getting official IP certification.
Last year the OnePlus 8 Pro got an official IP68 rating but the OnePlus 8 did not, and it sounds like we'll see a similar strategy next year. This is likely to help keep the cost of the OnePlus 9 down, though the OnePlus 8 without an official IP rating wasn't exactly cheap at its $699 launch price.
The OnePlus 9, 9 Pro, and 9E are expected to be announced in early 2021, possibly in March.