For the next seasons after the Season of the Dawn, the ideas will come from the community and Bungie as a collaborative effort. Ideas like weapon and armor designs and new activity mechanics will come from the community and Bungie is the one that fine-tunes it and then puts it into the future sandbox. Story ideas are the design for the weapons and Bungie will give us the idea they have come up with for that season. The community can design and submit their designs in ahead of time in order for those designs to be critiqued and maybe adjusted by the dev team and probably accepted even. That does not mean Bungie will also be left out of the picture, they can also throw in their own designs and ideas into the season too as they are the ones developing the stuff for all the seasons. This is a collaborative seasonal thing that I would really like to actually happen if Bungie does look and decide they need more ideas and look at the community for assistance.