I mean, I'm not saying that I don't think there could be more DLC than just the Fighter's Pass (I think an Echo could be a real possibility as a surprise along the way TBH), but I am for sure saying I don't think Nintendo made a definitive plan as to how many characters they were going to produce super early on and this many. If it takes over a year to just see five of them release, then we're talking about having a plan until almost 2022-2023. It's much more likely that they just made slots to basically act as an insurance for any reality moving forward so Sakurai can decide on his own terms without being necessarily bound to Smash for the next three-four years of his life.
A second DLC season seems to be a possibility for sure, but I'm going to really push back against the idea that those slots are indicative of how many characters we're going to get. 20+ slots is a damn high number of them, even with certain Alts taking up a theoretical slot or two.
Also,
Ovaltine
I absolutely meant to say it sooner, but Happy Birthday! It's a pleasure seeing you on the forums and I always enjoy reading your posts. I hope you're enjoying your day!