If it was arranged for Oda to take this time out months ago then it would be irrelevant what point the manga was at
the manga is the most important thing of his job. people here are acting like the manga is a side thing that could be disregarded because others are more important. his vacation will be mostly defined by the manga.
the break was decided months ago but also is the manga you think every week is a surprise and they had no idea months before when exactly the arc would end? oda usually has 3 chapters done before the publishing which means one month, if you add the story boards it is obvious they knew with a good anticipation when the arc was ending.
but like i said before this is based on the assumption oda and his editor will make logical decisions and they have proved in wano that is not a good way to predict their decisions anymore.