User experience, software supremacy and ecosystem integration is what moves units and moreso what keeps people coming back to a particular phone make and platform. The iPhone is the glaring example in my opinion. It's the package. It's updates. It's the promise of things just working. It's the promise of your digital life, physically existent in your phone, lying in the hands of one vendor, whose first and foremost product is software and services and not just hardware. The disconnect between hardware and software is what holds the premium Android segment back and what keeps Apple's iPhone ahead of the competition.
The reason I bought a Pixel is because it's an iPhone running Android. Samsung can introduce what they want, they don't own the platform fully and they're bad at software. Just look at the face recognition they introduced with the S8, which already turned out to be nothing more than a windy gimmick. Samsung, I can't take you seriously. With just providing the best hardware but the underlying software platform being a second thought, Samsung will never be able to overcome Apple. That's on Google who provides the platform. But Google isn't a hardware maker.
So with Samsung being the best hardware maker, to me it appears as a natural fit for them to just let the software differentiation BS go and team up with Google to make not only the most coherent Android handset there ever was, but also pair it with the best hardware and design (I don't think the S8 is all that perfectly designed, but what I rather mean is Samsungs ability and engineering-prowess to make the most sophisticated designs at a large scale at moderate costs).
They could even go on with their Galaxy line at full steam and see what works. And if their Pixel device happens to cannibalize their own offering, then so be it. On either side of the coin they earn from it. But with a coherent Pixel phone they might even seriously cut into Apple's premium stronghold in the long run.
With iPhones, people don't just buy hardware, they buy the newest hardware plug-in to their software ecosystem of choice. Google has the power to provide an alternative software ecosystem of choice and it should be Samsungs goal to be the delivering hardware vendor in tight collaboration.