You should continue to play if you haven't finished the main story so far or if there is a main quest that has a companion (like Hawkules) that you havent picked up yet. Finishing the main story so far will put you at an advantage when the next world comes out.
The current maximum level is capped to 65, You can still progress through the storyline if you hit the level cap early, but if you only do main quests you will only reach under level 60. I hope this helped!
What is the top level for now? Once you hit that level, is there any reason to keep playing that character?
I'm fairly certain you'll get a bunch of answers to this, but just in case.... The level cap is 65, is it worthwhile to comtinue your play? Yes, because the game isn't about levels, there so many things to do now. Pet training and pvp, companion orders get more gold, gear or sailing exp.
And of course a certain nefarious tower, that Ratbeard et al have been ceaselessly teasing us over!
One reason you might keep playing is to see how the story develops till you get to the current end.
I'm going to run my other Pirates up to the Level Cap. Then I'm going to get Nautical Experience up to max along with training Pets to their max. I'm going to "order" my Companions to go Brawlin' and Pet Wranglin'. So there are other things to do while waiting for the next major update to P101.
Of course, this can be done while helping other Pirates out (and you might get some Chests with Doubloons).