I am crazy hoping Wizards is bringing Pendleton in to advise on a new Gamma-Worldish setting.
I'm guessing that he's there to help with the next adventure which is their Alice in Wonderland inspired adventure. I could see Adventure Time ideas fitting well in an adventure like that. Plus, the adventure could start in the FRs but mostly take place in another dimension of some sort where reality is weird.If the next published adventure is going to be Adventure Time-ish it's probably not going to take place in Forgotten Realms. There's probably going to be the Planescape excuse where people can jump in and out of the potential new world we'll get in a few months. And if that's so, then we can finally have adventures outside of Forgotten Realms instead of adapting adventures from other worlds into D&D's "default" setting.
https://twitter.com/buenothebear/status/595384980160688129
The name of his secret project is "Dust". Which could allude to any number of things D&D-wise, but it's fun to conjecture. My thought is something lich/demilich related (as in the Lich from AT). Maybe a re-imagining of one of the Vecna adventures. It could very well be the Beyond the Looking Glass inspired adventure as well, maybe Vecna lives in some mirror dimension either trapped or as ruler.