At this point, it's probably too late for editing to save the series. Martin needs to start tying together story threads or the mess will continue and editing can't tell him what to write, it can only alter what he has already written (unless the editor has the power to force a complete re-write, which is highly unlikely at this point). If editing was going to save the series, it needed to happen in book four. That's when things went off the rails and Martin started world-masturbating. Before that point, he had plenty of time to handle the still large but manageable number of storylines running through the books. If Martin spends book six working on the white walker threat, tying together the Iron Islands, Dorne, Gendry, fake Aegon, and the entire north storyline, book seven could still be great. In other words, I don't expect much from book six but if Martin smartly starts reeling in past mistakes, it could lead to an amazing book seven. When I started reading book three, I started worrying that Martin was going to fall into a common writer trap, one occasionally displayed by even some great writers like Stephen King; thousands of pages of discordia wrapped up with a series-ending deus ex machina in the final 5-10% of the book/series. Thus far, Martin has only fueled that concern. But it's not too late to fix it, I'm just not sure he realizes it's a problem... Though with how well the show has played out in season six, I hope that was a wake-up call to him.