Cragio85 had some good points though. Primarily depends on what Apple will have available stock for the OLED model. Given the fact this will be a major redisign with all new features, the OLED model will be back ordered for months. Guaranteed. And $1,000 OLED iPhone will be broken into payments. Most won't even consider the affordability, because they want it that badly. Period.
Sure, the 7S will have its core demographic who are not interested the OLED model for a cheaper entry price point, but factor in the hype, demand, Apple's supply chain restraints (Which happens at every launch) for this new 5.8 OLED model, good luck even trying to Obtain one if someone doesn't preorder. And let's not forget, it has an Apple logo on it concocted with a new model iPhone, it will be pure madness for the demand. That's a fact, and Apple knows it.
In the end game, it's the latest and greatest. The sole attention will be on this OLED model, not the 7S, even if it's "Selling more." It's not much of a secret where the sole focus where a newly redesigned iPhone that will shatter numbers in terms of what someone wants, When a second thought doesn't come to mind what someone can afford. Supply vs demand. Demand will take hold with the OLED model. Simple logic.