I don't think they'll ever get it. It's over twice the distance of D-Day, under worse conditions (only 4 months out of the year it can even be attempted) with contested air and seas (we owned the air and sea at D-Day and every over D-Day thereafter). Korea is just a man-on-man slog where all they have to do is send them across a border. All of this ignoring their political goals (viability) re. Taiwan.