I assume they'll replace it with something just slightly modified -- "Proud to fly Boeing" or "Proudly flying Boeing for xx years"

I also wonder how soon that white tail A321 will get an eskimo on it -- but painting tails is very complicated, as seen in the shot above, it has to be done before being attached to the fuselage. I don't know if they can get away with using a decal on a tail as an interim step...?