I'm not sure how long it will take for the first 20 stage pack but what I can say so far I've done 2 Stages... Although I feel as if I've been a bit slow as of late... hmm...
Anyway besides the 20 stages I also want to sprinkle in a bit of lore and story in sorta/kinda of a hub world but that can be largely ignored for those uninterested in it.