I'm pretty sure that Leaks said not.
Also, I think they've started with a really strong set of headliners (although I still think the undercard is weak af).
They have the opportunity to book a slightly more interesting headliner than being 'safe' with Dua Lipa for the third time in six editions (that said, I would still be happy if she was announced!)
That's the assumption, yes.
For scale, I recall there was a brief phase where BST Hyde Park would show a few songs from some but not all headliners on Sky but even that now seems to have bitten the dust.