Pssst! Go look at the Planet Coaster release date, and the release dates of those DLC packs. Now go look at all the Planet Zoo release date and date for the one DL C that is currently available. Quite similar and maybe quite easily predicted -wink-
Like almost everyone else, I am aware of that. Hence why I said "it's definitely getting to that time" - sorry, I thought it was implied. They might not stick to the same release schedule though, a fair bit more goes into the animals than goes into rollercoasters and flat rides.
We might end up getting the same number of DLC's spread out over a longer time, for example, or fewer DLC's. Or maybe even Christmas releases. I suppose my biggest worry would be that they see stuff like this (people asking about the next DLC constantly) and then try and rush out an infinished product to meet demand.
Edit: I should also point out that the Arctic Pack was released for Christmas. We probably would have had new content at Christmas time regardless of whether or not Planet Coaster did it, because Christmas is a retail holiday and it's common business practice to get in on those Christmas sales.