Do I need to pre-order the physical version to get the Season Pass or can I just buy it Day One and still get it?
It's a real bummer that there seems to be so little interest in the game. All the videos on youtube barely have any views.
To quote the words of SNK president Koichi Toyama:
"As a thank you to the fans who have stuck with us during the long wait between the franchise installments, we're pleased to offer the first six months of DLC completely free of charge to anyone who buys the game and redeems the game's season pass within the first week of release, which will include four new fighters."
That statement doesn't explain 100% how the system works during that first week, so if I was you, I would pre-order a day before release to avoid any complications, just in case.
As for the low interest in the game, I think a lot of it is riding on how it performs at EVO. It has quite a lot going for it, the gameplay promotes high stakes gameplay, where the tables can turn in a single move, which makes it very suspenseful and exciting to watch. It also has a very deliberate movement system, that slower speed makes it easier for the casual spectator to understand what's going on... If it gets enough eyes on it, I'm sure it has the potential to be pretty popular.
We can't forget that Samurai Shodown isn't as famous as Street Fighter or even The King of Fighters, but the fans who do know the series will very likely buy it, even if it's just for nostalgia's sake. But I do have trust in SNK, mainly for the fact of them taking their recently announced and unproven new fighting game to the floor of EVO 2019 as one of the main events. That takes a ton of courage, so they must have a lot of faith in the quality of Samurai Shodown.
At the very least, I think the timing for releasing this game is just perfect. Sekiro and Ghost of Tsushima are putting samurais and ninjas back in the spotlight, and with Street Fighter V being in a bit of a slump at the moment, there could be no better time for Samurai Shodown to make a comeback than now.