(Spoilers Extended) a set of Winds of Winter chapters completed and sent to a cartographer (map maker). "actual parts of the - - - - - - - map are directly involved with Winds of Winters" - Jonathan Roberts. He confirmed which character's POV he was sent.

George started working on the Braavos map back when he was writing AFFC before 2005 (wasn't the Mercy chapter suppose to be included in that book before he split it into ADWD and moved Mercy? ) So as George wrote more books, the Braavos map started to change and evolve and he hired Jonathan Roberts to recreate a new Braavos map (for the book "The Lands of Ice and Fire") and he confirmed this:

"I got chapters of 'Winds of Winter', which was very nice. Now just to give you an idea, this is 2012. There were finished chapters of 'Winds of Winter' in 2012. I'm not going to say any more. So actual parts of the Braavos map are directly involved with 'Winds of Winters'".

Ckram has done a great job putting everything together and analysing the new map here: Link

In fact, Roberts said that the map of Braavos in TLOIAF was accurate to the point that one should be able to trace Arya's routes precisely – "right down to the individual bridges she passes under". He also said on reddit that this map "has the most specifically new material in it".

So why the hell we don't have a single map of Winterfell, Meereen or Oldtown but have such a painstakingly detailed map of Braavos if not because something really major is about to happen there in the next book?

On Jonathan's official site he said, "yes, look at this one carefully – there are locations on here that haven’t appeared in the books … yet."

Ckram has spotted 10 unnamed buildings highlighted here:

https://asoiafbr.files.wordpress.com/2018/07/50224da4-524f-4ff8-897f-25155efc2bf4.jpg

Full map in HQ:

https://i.imgur.com/wSwrFb9.jpg

A few days ago Jonathan was asked outright:

Q: Jon, I have a question about your Braavos map. You said you were sent 'chapters' of Winds of Winter. However, in a Google Talk video about TLOIAF you only shown one chapter of that book in your harddrive, 'Arya I'. I not asking for spoilers or anything, just if you can at least clarify if you received more than one chapther of WOW? Thanks in advance.

A: it’s actually all the Arya chapters. Not just one.

👀

Another change he confirmed was the added green isle to the Sealord's Palace requested by George. As these new changes will have implications to Arya's Winds chapters, we can confidently assume she will be a POV of that location. Perhaps also confirming where in Braavos Dany spent her early childhood years with her lemon tree and red door? The Sealord's Palace? How would George get Arya into a position where she could enter such an elite circle of people? Possibly seeing other locations like the Palace of Justice or the Hall of Truth?

All that coupled with all her duties with the HoBW and her eventual fall out from the FM, interactions with fArya Jeyne Poole, the upcoming election of the Sealord of Braavos where all the knives will come out 👀 and to top it all off the yearly 10-day Unmasking celebration that marks the day Braavos stopped being hidden from the world. Perhaps another Starkling will finally do the same and stop hiding who she really is.

One last thing to point out:

Jonathan was sent all the chapters George wrote of Arya related to Braavos as they would help influence his newly created map. However, we also know George has continued to write new WoW Arya chapters after the ones he sent to Jonathan. (George later confirmed he was writing an Arya chapter at a Q&A in Chile) Is it likely these are new possibly non-Braavosi chapters? Perhaps with Arya already returned to Westeros.