I really don't think a rebranded 480 (580) will ever be able to beat a 1070. Just look at how the 300 series panned out. Not much changed from its predecessor. Considering the modern times and the performance level of the 480, AMD are in a hard spot with the rebrands. They really can't release a 580 at the same sorts of prices as a 480 released at. Heck, especially not when we had 480s going for as cheap as they have been recently. If they want to keep a £200+ price point, they really need to offer something more, but I'm doubtful a rebrand could do the trick.
Otherwise, those who bought their 480s at sub-£200 prices recently will have gotten the best of it for a while. Not much reason for people to upgrade if they've already got the same sort of performance for cheaper already.