The lvl cap is lvl 400 TM lvl 500 on jTO.
Also, no they don't need to put in a whole new island and raise the cap to 800 unless that new island has quests that functionally help you get to lvl 800. The highest lvl quests they have right now are lvl 290, when they have quests that are lvl 390 I'll start demanding a cap increase.
Next there will be no 4th job ever! There's no way they could functionally make a 4th job at all. It also doesn't fit the back story of the game.
and finally your suggestions are better fit for this thread: /forum/trickster-onl...ke-better.html
this thread is for posting actual things that other versions have, not what we want the game to have.