If they were playing Glastonbury, it would be an incredible exclusive thats for sure. Since a lot of acts performing around those dates and other festivals are all booked, and nobody is saving a surprise headliner or addition at this point. At least NIN being an Other Stage headliner it most likely places them against Ed Sheeren on Sunday, cause youre not placing NIn against Foo Fighters or Radiohead, thats too much similarity, and Glasto likes to give you vastly different genre alternatives to the top billed acts.
The only Gv festival left to announce if it even happened would be Desert Trip. But NIN does not belong anywhere near that event anyway. If they did sign on to play Coachella next year, then so be it. Theyre usually booking the headliners at least a year in advance nowadays anyway. Sandwiching NIN in between Beyonce and like Daft Punk would be perfectly fine. I would not be surprised if they did these 2 dates and thats it. They could maybe test out some of the ep material, or just see what the future touring production is going to be and make some tweaks. And considering the kind of budget GV has in regards to booking acts for their festivals, I doubt they are flinching one bit with production costs. And you know we should consider if there is a proper tour, its announced after FYF and Panorama are done, which still gives plenty of time for onsales and such.