Since we are jumping from a thread to another thread to discuss about potential DLC so I presume that it's a time for us to trying to get us a home where we could discuss about future contents.
Currently Piranha Plant and Joker are out for us to purchase so we are still waiting to find out those four characters that would take their places in Fighter Pass. Our next hype stop would be at E3 for sure so it's quite exciting for us to find out who would be second character and potentially third character if we are lucky. Also there is a detail that specifically confirmed that we are getting more Mii Costumes as part of their DLC plans. Our previous question was; Are we going to get more contents than we are expecting? Beyond Mii Costumes and Fighters Pass? Yes, we did. We got Stage Builder and Share Function (where we would download stages, mii fighters, etc online.) Some fans are still hopeful that we would get more mode(s) in the future updates.
RUMORS
There are multiple rumors about Downloadable contents but I urge you to take it with grains of salts. Nothing sets in stone until Nintendo 100% confirmed those details or the leaks itself is somehow very convincing with reliable access to images or/and video. I guess there is only reliable information we had on second downloadable character which had a codename which named as Brave. Most common guesses around here is that they strongly believe that Brave is a main character named Erdrick from Dragon Quest franchise.