Well, I hate making predictions because the one constant is how unpredictable crowds are, especially because so many factors are announced/happen last minute. Ticket deals, special events or offers, weather factors... these can all render the wisest, soundest predictions completely useless.
I wouldn’t go in January for a bunch of reasons, but if I make that a firm recommendation, I’m sure it will somehow turn out to be legendarily low crowds and you’ll be all, “curses upon that skyegirl1999 and her bogus predictions!”
February has been the “Monday” of the year for awhile - the weird time everyone expects to be empty, but isn’t. I honestly talk to more unhappy tourists in February than any other month by a long shot. But, with ROTR, probably no one expects it to be empty? And theoretically they’ll be prepared for crowds? So who the heck knows what will be up with February.
I like March and I love June at the parks. June is your best bet for the best park hours, which are more important than you realize (8am openings are key to life, especially since you’re not planning to stay late... although I’m still thinking that could change in a year). ☺ But that’s also a whole year away! So long!
So, I’d probably stick with March, but don’t quote me on that and don’t be mad at me if March turns out to be the worst.