The camera to bring Apple back to the top will be revealed on the iphone 7. Apple knew that they're "tied" for the lead right now and Android hasn't clearly surpassed it. They are willing to take a little bit of heat for a year and say "we're tied for the best." And then go for the win next year with the 7.
DXo, I will say, does not seem to look at the actual pictures at all. I never understood why Sony's cameras are considered good. They're absolutely not top tier cameras. Have you ever looked at the pics produced?
Samsung, if you actually look at the pictures, are the best, right up there with the iphone. Maybe LG G4. That's it. It's a 3 horse race and choosing a smartphone for people whom camera quality is paramount is a rather easy decision.
But I will say that DXo seems to be consistent. When Apple announced just a 12 megapixel sensor upgrade and nothing else, I figured that the camera would perform identically. So receiving the same score seems fine to me. There's no reason to expect the 6s camera to improve from the 6 camera. It's like 1-2% better max, and any benefits are from software processing tweaks that are firmly in the area of personal preference.