It‘s not confirmed, so we can’t be sure until WWDC. If they drop support for the iPhone 8 this would also mean that they have to drop it for the iPhone X as well and that would be a shame. The 8/X got 5 years of software updates and the 6s got 6 years. So there might be a chance for the 8/X getting iOS 17. But I don’t expect Apple to support iOS 18+.