I called the other day - it was no big deal. I reserved room for our 2021 vacation. I can apply discounts later and also convert it into a vacation package.
I booked for Jan. 2021 yesterday. Yes, must be by phone. After answering a couple robo questions, I had a live person immediately. That’s right...no waiting. I wasn’t ready for that.
I have a room only booked for Feb--have to do it early because of the kind of accessible room I need. When packages and resort military discounts come out I will call and rebook. I always call, for two reasons--I want to keep people employed and they can better find what I need in less time than I can trying to do it online. I am enough of a luddite that I don't even like doing fastpasses or ADRs on line.
I would def call because there's a chance you'll get a different rate than the final 2021 rates they publish in June - if it's lower, great, if its higher, you can rebook online.
This is not the way it works. If you call now, before the 2021 prices have been released, you will be able to book a room up to 499 days out, but you will be quoted the current rack rate, and have to pay a deposit of one nights room + tax. BUT this rate is not locked in for you. Once the 2021 rates are released, the rate for your reservation will be adjusted accordingly. If the 2021 increases from the 2020 rate, you will be charged the new 2021 rate. You will also receive an email or call asking you to increase your deposit to bring it up to the new one night + tax rate. You don't get a break just because you book before Disney releases the next year's rates. If, for some reason, the 2021 rate decreases, you will not be refunded that difference between the deposit amounts.