As mentioned in the 2025 Headliners thread, The S*n - and since picked up by others - say that album number six is imminent.
They also doubled down on them being Glastonbury headliners, though there does seem to be some speculation they are out in favour of Sam Fender.
I'd prefer The 1975 to Sam Fender, but that is very much a close-run thing. For me, unless Harry Styles pops out of the woodwork, not sure there's any British act bigger than either in the headline conversation who haven't done it before among current chart contenders. (Have touted Dave a couple of times and I guess now that they are about to be out-and-out R+L headliners, you could put BMTH in the conversation, as unpopular as that may be.)
I think I am just looking it from a UK point of view, that order would make sense here.
You might be on to something though, NIN before Kings of Leon would be pretty good