Reports of the OP3's demise appear to be greatly exaggerated

You may be right about that price point. But if so, I think it may be a harder sell unless the rest of the market similarly ups their prices.

I would have thought smartphone pricing in general would have headed downward, not up as the market matures. You can get a lot of laptop for the price of flagship phones these days. Shucks, you can get a lot of laptop for the $400 OP3 price point

The phones I considered in my shopping this year were in the upper $800 range (iP7+, Note7, Pixel XL, etc.). But spending that much $$ for a phone not supported (OS and security updates) more than a couple of years simply did not make economic sense to me. The iPhone is the standout for long term support and my main reason for iOS interest. Even the Pixel drops OS support after 2 years. But I just couldn't make the iOS move. I see enough of that on my iPad mini2.

So to me, the value buy became the OP3 with a near pure Android experience and a reasonable price that would hopefully allow me to upgrade in a couple of years and, after buying 2 phones, still be below the 2016 flagship price point. But if OP is pricing upwards, then my strategy may fail. Regardless, I may be a few bucks north of a 2016 flagship in a couple of years, but still have the latest HW. So maybe it still makes sense as long as OP pricing remains "reasonable".
Yeah, before I thought I would definitely get the Oneplus 4, but now I'm gonna look long and hard at what ZTE, Lenovo, and even Xiaomi put out. Hell, I might even glance at LeEco.