If you go to Poptropica now you can see that there is a small promotion in the bottom left corner for a Haunted House. All it says is coming soon, and you can’t click on the promotion. It’s definitely for Halloween (of course!) so it should be coming out really soon. It’s probably going to be a mini-island so not quite as long or complicated as something like Astro-Knights island. But it will probably be spooky and fun!
In the meantime, there are also new costumes that you can get in the Poptropica Store. They are a Frankenstein outfit, a Bride of Frankenstein outfit, and a Pumpkin Head outfit.