One thing that kind of scares me is that, Ok maybe all of the evidence for porky is there but Sakurai didn't pick the dlc. Why would Nintendo care about missing spirits and if he was a past boss or even the year of the pig. Common sense would be to use the characters for promotion or something. I was surprised with Joker because I thought he wouldn't be a promotional character but later on Persona 5 of course got new content and is basically confirmed to come to switch. So yes, Joker was promotional. only way I see Porky is if we get something Mother related so that he could be used for advertisement. Nintendo only wants to sell games while Sakurai gives even dead series' love.
Maybe thats why he went there tho, why on earth would he go to a old poster of mother 3?
Maybe nintendo picked him and he wanted to hint at it a little bit? But you have a point, maybe he just went to pay respect to a dead franchise.
One thing i would like to hope for is a pattern. We had pirranah plant, a villain, and then joker, a hero. What if its a pattern? Villian, hero, villain hero, villain, hero. It would help, since they said they wanted more villains, and a few 3rd parties still havent gotten villains that could work (cloud with sephiroth) (sonic and eggman) (yes i know spirits but we have yet to find out if spirits deconfirm fighters), so we have yet to see what will happen. Lets just hope june or july we get our chubster announced