If they keep the casing the same size and go no-bezel on it, it'd still be reasonably usable, but you'll need Reachability to get the top of the screen one hand

If they keep the casing the same size and go no-bezel on it, it'd still be reasonably usable, but you'll need Reachability to get the top of the screen one handed. 4" diagonal is about the max my thumbs can cover.