It feels strange that Apple is making such a profit with a rather smallish that may be 12% of the market and no particularly eye-popping new products since the Steve Jobs era, just a series of well-engineered refinements.
I think you underestimate the "eye-popping" value of the 6 Plus screen size among consumers. I've owned every new iPhone since the 3GS and despite waiting a couple of months after the release date, still had a backorder time of 6 weeks when I ordered a 6 Plus. That hasn't happened for any other model.
It may not have been an eye-popping change in absolute technology terms or geek credibility, but what would be and would consumers care? There's too many constraints on size and battery life for more much more than incrementalism.
Plus I think all smartphone vendors want to maintain the current niche paradigm for these devices -- the consumer understands the "role" of the smartphone in their larger electronics ecosystem.
I think it will take someone willing to gamble on the idea of a dockable phone that can be used with KVM as a PC and/or tetherable to a "screen only" tablet to really shift the paradigm a lot. Apple could do it since they control the whole ecosystem but likely want to protect their product segments from sales loss, x86 is too power hungry and Windows failed on RISC and with Metro.
Google seems likely since they aren't specifically tied to given CPU and so much of Chrome is web-focused. Maybe Project Ara is sort of the start of this to sort out the modularity aspect so that you can assemble an Android/Chome system from parts or dock components with other components.