According to one insider source: "Samsung poured resources into Synaptics’ fledgling technology last year but the results were frustrating. With the production imminent, the company had to decide to relocate the fingerprint scanning home button to the back of the device at the last minute." There you have it. Synaptics is indeed talking about in-screen finger sensing at a preset area as the current step in its developments of the technology, which would imply it is still not completely out of the testing phase, while the next and final step would be placing a finger scanning area anywhere on the screen that the manufacture chooses.
That's still some time off, but, given that Apple will have a bit more time before it announces an eventual OLED iPhone 8, we are curious if it will have the in-display sensing tech that the Galaxy S8 eschewed. That could steal a bit off the Galaxy thunder, but Apple has never been one to jump on nascent technologies ahead of the pack before they have been proven in the market, so we'll see how it all pans out.