DHS will be insanely busy, especially on weekends.
Epcot will be insanely busy on weekends for F&W.
MK will be less than prior years.
DAK will be less than prior years.
Water parks will be empty on weekdays.
I agree with what is posted above. I'm looking at the site (mid September) and there are plenty of all-star rooms and non Epcot/HS resorts available. The Epcot/HS resorts (besides Caribbean Beach) are booked.
I don't think it will be bad. September is typically softer (beyond parties and Food and Wine), and with Galaxy's Edge opening (and the crazy early morning Extra Magic Hours every day), I suspect the focus on DHS will make it fine at the Magic Kingdom.