Reports are that Google will be announcing two new smartphones in October that will have Google's Pixel hardware branding rather than the Nexus branding. 

Nexus phones are developed via a partnership between Google and a select hardware partner that have a pure Android experience, are directly updated by Google, are sold on Google's store, but are branded such that it is clearly known who is the hardware manufacturer. Nexus phones are not truly Google phones. For example, the Nexus 6P is a Huawei phone and in fact you can order a Nexus 6P either from Google or Huawei. 

Pixel came into existence when Google announced, and later sold, the original Chromebook Pixel. The Chromebook Pixel was clearly Google hardware and it is not obvious who actually manufactures it. There is no partnership with Pixel products, they are sold as Google products although clearly manufactured by some other company.

If true, the new Pixel smartphones will be a little unique in that we appear to know who is manufacturing them for Google, reports are it is HTC. If the past is an indicator, the Pixel phones will be only sold on Google's store and will only have Google branding. 

From the beginning, Nexus has been about partnership and leading the Android smartphone market. Part of that partnership was an attempt to influence how Android phones were developed. My guess is that originally Google hoped their hardware partners would decide to just use the "stock" Android software and updates and focus on hardware as a their competitive advantage. 

Unfortunately, while they were able to work with several different Android smartphone manufacturers over the years, none of those manufacturers decided to transform all their products to stock Android. Worse, Samsung and others have articulated their desire to use other smartphone software and not rely on Google at all. 

Consequently, I think Google has decided to give up on the idea that they could influence the smartphone market via the Nexus "program." Instead, it appears they have decided they will sell smartphones are that are clearly Google phones (In a way returning to the original G1 branding) and in essence be competitors with the Android smartphone manufacturers.