Boeing Board of Director gave BCA the ok to enter into discussion with customers on the pricing, delivery, and technical aspects of the 777X a third generation of the large Boeing twin. With this ATO, Boeing now has 2 large twins with the Authority to Offer to customer airlines but Boeing still needs to formally launch the aircraft once they have acceptable deals in place for each.
One question that still remains is where to build the 777X and especially the wings which Boeing plans to construct from composites (CFRP). More than likely I expect that both the aircraft and the wing would be built in Everett due to the expense of establishing a new final assembly site along the difficulty of transporting a large wing from site to site.
I do think that it is not unreasonable to think that both the 787-10 and the 777X can be formally launched at the Paris Air Show though it can also happen at the Dubai Air Show in November.