David Kanter wrote a piece about the future of mobile CPUs for ARS Technica, you can read it over here.
In the long term, mobile devices are likely to evolve similarly to the PC and favor a horizontal business model. The real advantage is one of flexibility; as costs drop and the market expands, it will be increasingly necessary for vendors like HTC to offer a wide range of phones based on radically different SoCs. While a vertically integrated company like Apple can focus and maintain leadership in a specific (and highly lucrative) niche, it would be very difficult to expand in many growing areas of the market. The differences between an iPhone 6 and a $20 feature phone are tremendous and would be very difficult for a single company to bridge.