As an a7Sii owner I couldn't agree more (the D850 looks great too). Phone cameras are going to have a hard time catching up there. There's only so much light and at some point, sensor size matters.
In my GP comment I mentioned being amazed by my friend's iphone 7+ pics, and it's true, I was. But when the sun went down, the a7Sii ruled over everything and captured every good picture from then on. There's a long way to go for the mobiles to be able to compete at night. Nice to know our investments aren't totally useless :P
No matter how you cut it, that's generously 1/10th the sensing area/capacity (same thing). And it's not like the sensor tech in the iPhone will be 10x more efficient than contemporary DSLRs - iPhone sensors are made by sony, who will use the same tech in their own cameras. To get comparable light cell for cell into that you'll need a lens with 10x more light ingress, and sophisticated optics to focus it precisely down to a tiny half-square-centimetre. This lens would be larger, heavier and more expensive than the phone itself. Think "large can of tomatoes" size.
Not saying it's impossible. Mobile phone companies have pulled off some amazing advances and I have no idea what tricks might be up their sleeves. But for now, no mobile even touches full frame DSLRs in low light, and it doesn't seem like an easy hill to climb.
Also, focus stacking!