Jimmiesatx-
As far as Christmas things being up in early November, I'll try to break it down (it happens in stages! lol) as clearly as I can (it can be confusing!)...
Some holiday season decorations begin to appear even before Halloween, or at least they have appeared pre-10/31 in the past (something could always be different in 2018, though). That includes, but is not limited to, the Mardi Gras masks in New Orleans Square and the fake "snow" on the Winter Castle in
Disneyland.
Haunted Mansion Holiday stays open all the way through Halloween Time and the Holiday season, though there is a bit of a question as to what its fate might be by 2018 (if the majority of Halloween Time offerings move to California Adventure, which is the rumor). So, I would say that HMH should most likely be open when you take your Nov. 2018 trip. It's a Halloween Time and a Holiday season tradition, and is extremely popular, so I don't know if Disney would remove it from the 2 seasons completely due to more Halloween things in California Adventure.
It's a Small World closes within the last couple of weekends of October, for the installation of the holiday season overlay. It's a Small World Holiday is one of the things that has frequently soft opened before the official holiday season start date. So, for example, if the holidays were to start on November 9th next year (that is not a given, just a guess), IASWH could be open as early as 11/2, or anytime prior to 11/9. (The holiday season starts on 11/10 this year, and I expect IASWH to be open before that date.)
As soon as Halloween Time ends (which is usually 10/31, but there have been a couple of rare exceptions over the last decade), the Halloween decorations on Main Street begin to come down, and the Christmas decorations go up. Space Mountain Ghost Galaxy closes for overlay removal.
If ABC does any kind of holiday taping -- like of the Christmas parade, for example -- they would tape on the weekend before the holiday season officially starts -- which is why the park has to get in Christmas mode rather quickly. They can't film a Christmas parade against a backdrop of pumpkins, after all!
So, let's just say the holiday season begins somewhere between 11/9 and 11/14 next year (the season has started on weekdays other than Fridays in the past, so anything is possible again). I think you'd see a lot of decorations up and possibly a soft open of IASWH prior to that start date, but some things won't be in effect until after the season begins.
And then other things like the hotels' decorations will not be up until after the holiday season starts, but not right away. In some years the hotel trees have gone up about 9 or 10 days before Thanksgiving, but that might not be the case every year, depending on how late or early Thanksgiving falls in the month, and relative to when the season officially starts. For example, if the season were to start on 11/9, I don't think the hotels would be fully decked out in holiday splendor on that date, but if the season were to start on, say, 11/13, I think the hotel decorations would start to go up very soon after that date. The Grand Californian Hotel's gingerbread display (in the lobby) is assembled in the week leading up to Thanksgiving, if I recall correctly.
