I believe that base roster is already completed by Nitnendo, since the game launchs in 2 months and Nintendo needs to sends it's informations to maketing people, magazines and guides. So, I also believe that even if it takes some time until Nintendo reveals some DLC it is already working on. With Nintendo Switch Online needing more acceptance and visibility I think the DLCs will arrive faster this time.
DLC won't help advertise the online service, as you only need that to play online, not to download DLC--charging people to give you money is counterintuitive. Beyond that, you're right that the base roster is decided already, but the game is not yet complete, as Sakurai said he hopes to go gold "soon." And even if DLC were already being discussed, no leaker will ever have info on that during the decision phase; remember, there was not a single leak for
three years after Ultimate's roster was finalized in 2015. Any info that anyone has will come from leaked presentations and the like, meaning only a few weeks or so before Nintendo releases the info themselves.
That being said, could Nintendo be planning to reveal DLC plans in the next two months? Possibly. But I doubt they'd have much to say, as I don't think Sakurai has even touched DLC discussion yet, given Bill Trinen's post-e3 comments on how determined Sakurai was to getting the game finished first.
In another month or so I could see Sakurai finish the game and move on to DLC, but that's not enough time to have literally anything but a list of names ready to show the public, and that would be a HUGE mistake to show without seeing if A) Sakurai can actually make a character work and B) if he can actually get the rights to any particular character (As many are said to be guests, remember.) Recall Sakurai has stated it takes about a year to create a newcomer--a few months is NOT enough of that time to have anything to show or indeed confirm at all. And before you cite Mewtwo, remember that he had been planned
before DLC in Smash 4 was considered. He was a character planned for the base game, but they lacked the time to create or even start him. Him getting a reveal was sort of like cheating, if you will.
So long story short: it is TOO EARLY for DLC.
Now, if you want to consider rolling updates like with ARMS, I could see that. That's actually a trend in recent Nintendo games, especially competitive online ones. It's something that could be planned ahead of time as well. But that depends on Sakurai, and we know he likes to give people a complete package to start. The reason we get rolling updates is to get the game out sooner and keep people playing. But those games often seem incomplete on release. I don't foresee Sakurai letting Smash feel incomplete.
All that said, I do agree that DLC is a source of hope for many characters. I've said that from the start. But please, people, let's not count our chickens before they hatch.
