Thanks to Dr. Jack over at the Korean Lost Fourm, the final billboard image has been found, that gives us a total of 9 billboards! (click to enlarge)
The ODI has enhanced the image by zooming into the Korean text, and also has the translation from FoxySmile:
“The first sentence on the Seoul BB is the same as the one on the LA BB, ‘The adventure begins here’.
But the second sentence, ‘Your ultimate destination’, is translated in
Korean as ‘You (have) arrived at your ultimate destination’… I don’t
know that it really means something or it is just some the wrong