Don't Wait If You Find Something Great
Don't let the HTC U12 hold you back though. If you find something you love or that interests you right now, get it. Or, if you decide on something like the affordable OnePlus 6, don't spend more time waiting for a phone that still isn't official.
If you find a phone like the Galaxy S8 on sale or a great deal on the Galaxy S9, get it. They're great phones with a lot to like, great screens, and a similar amazing camera experience. Not to mention most carriers allow upgrades once per year now, instead of two.
So, you can probably get the HTC U Ultra or something else that's from 2018 without spending too much money. And while we're expecting great things from the HTC U12+ and an improved "Edge Sense", we don't know if it'll be worth the wait. Even with four cameras.
At the end of the day, find what you love, and use it. Don't wait for the "next best thing".