If it was not an April Fool’s Joke, and that the maximum Hunter Rank actually is being raised to 400, then
a) I hope that players that already reached HR 300 get their efforts made since reaching HR 300 added to their new rank (so that someone whose extra effort made since reaching HR 300 would take them to HR 350 immediately gets promoted to HR 350) and that the additional effort is not discarded
and much more importantly
b) as has long been requested, the rewards for the daily quests should reflect the Hunter Rank, and not just stop at 100, or at whatever point it is that the 1000 Zenny rewards change to 2000. It should be something like
1-100: 1000
101:200: 2000
201-300: 4000
301-400: 8000
Otherwise it’s just a song from 1981 by the Anti Nowhere League.