The 2nd batch of Halloween Screens may or may not be scrapped. That's up to Oda himself. As for Tati's contest, it will be put in after the Christmas ones just to stay on season.
I personally feel each batch should be in game for at least 2-3 weeks, at most 4 weeks and not longer. Considering the regular loading screen submission have been backed up too, and we would still like to see more new arts being put in.
I will continue to help with streamlining the loading screens being put into the game on a timely basis. Oda wears a lot of hat managing this game, so please do forgive the hiccups.