According to serebii, Corocoro revealed these new sillouettes..
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The first picture is Zygarde Cell. These are parts of Zygarde that are scattered around the Kalos region. They watch over the ecosystem in Kalos and are pretty much useless really
The second image is Zygarde Cell. These act as Zygarde's brain and function similarly to the cells. They can use telepathy to communicate with other cores and cells
The third image is 10% Zygarde. This is when 10% of the cores and cells merge together to create this form. It is capable of traveling over 60 mph (100 km/h), it defeats enemies with its sharp fangs and its incredible speed. 
The Zygarde we all know is 50% Zygarde.
Finally the final picture is Perfect Zygarde. This is when 100% of the cells and cores merge together. According to the magazine, when the ecosystem is under threat, and the Core concludes that the 50% Forme will be unable to deal with it, the Core takes on the Perfect Forme. Its power is said to be greater than that of the Legendary Pok?mon Xerneas and Yveltal!
These are all forms of Zygarde and maybe we will get something new in November!