Hm, yeah a stamina spell might be a really good idea actually. And yup there will be a sort of final boss and there will be stuff involving the person you see at the bulletin board eventually.
Oh, if you mean the people at the pier then you should still be able to see them again. One of them only appears in the evening when the sky changes colour, and the other two should usually be there every night.
Also the Kangaroo will be at the Castle area.
And I see in another comment you were asking about the Wario Pill and the Halloween event. The Wario Pill is still in the game - it's a drop you can get from beating the shark. And for the Halloween event, finding all of the items should be pretty straightforward. There's one aspect of the update that might be tricky to figure out, and when you get to it I'll answer any questions - I just don't want to say too much about it though because I want that to be a surprise