Don't Wait for a Waterproof iPhone
Nothing is confirmed, but it looks like the 2019 iPhone design will share at least one thing in common with 2018's models.
According to Apple insider Ming-Chi Kuo, the 2019 iPhone will feature the same IP68 water and dust resistance as the iPhone XS and iPhone XS Max.
If you're not familiar with their design, the 2018 flagships are both water resistant up two meters for 30 minutes. It's an improvement over the iPhone X, but Apple could go higher.
So if you're hoping the company adds water resistance up to three meters or more to the iPhone's design, you might want to temper your expectations.