Finally, a true intellectual topic.
I'm gonna take my pipe.

  Mmmm... Goku, indeed...

I really love Goku, but it's true, they're going to ask for Vegeta, Luffy, Naruto, All Might...
I think it's more likely if Sakurai isn't involved in the next Smash, I'm not saying it's likely, just that it increases the probability just a bit.

What kind of crossover is Smash? If it's a Nintendo crossover, Sonic and Snake broke that in Brawl. If it's supposed to feature only characters from E-rated IP, Bayonetta broke that in Wii U/3DS. If it's a crossover between characters that aren't from traditional fighting games, Ryu broke that in Wii U/3DS. If it's a crossover between characters that were prominent on Nintendo consoles at some point in the past, Cloud broke that in the same game*. If it's a crossover between Japanese IP, then Banjo & Kazooie and Steve broke that in Ultimate. I guess the only supposedly hard rule left is that its a crossover between characters that originated in video games. Why we have to have this arbitrary rule to preserve some sort of sanctity, I don't know. I just want everyone who thinks that rule should be upheld to imagine Ultimate with the original rule of Nintendo IP only, and if you feel like that would make it a better game.

*Miss me with your counterpoint about Theatrhythm on 3DS. That's not a real Final Fantasy game.

What's with the hard take unsubstantiated by an claims, proof or reasoning? Why won't Goku ever come? At least explain why. Please explain what this mythical franchise foundation is too.

Is Dragon Ball Z popular? I've never seen it, but I remember my college roommate used to like it.

Not my job, I will let time answer that 

^THIS!!

Dragon Ball sucked after Z ended, anyway. *slowly feeds all Super era characters feet first into a wood chipper* I miss Toriyama, but he made mistakes.

I wonder how many of the "No Goku" people fall into the "I'm just going to mostly play Melee anyway" type crowd?

If the character is wanted by new fans, then they should put it in. The series has broken the forbidden door and has let in a number of characters who don't belong to Nintendo and originated on other consoles. Wouldn't be my pick, but I'm unlikely to buy anymore new Smash Bros games until something drastic changes with them - something Kirby Superstar level - which they kind of dipped into with Brawl, but could have gone further. Incidentally, Brawl is the only Smash game since the original I got into.

So, I'm OK with having Goku or other non-Nintendo games put into the game, especially if there's nothing else coming to change and advance the game series. But personally, I want some significant additions to the series before I'd consider purchasing any more Smash games.

A lot in Europe (at least, some parts of Europe)...  during all the 90s XD

In USA Dragon Ball arrived in early 2000s (failing to get any success in the 90s), when the series were already finished in 1997. By then, was an old product in Europe. But Bandai started to produce and granting licenses of new games, because the US delayed fever, in 2002.

So the new wave of games reactivated the interest of some. Before the first Budokai game for PS2/Gamecube in late 2002/2003, the last game was "Dragon Ball: Final Bout" from 1997 for PSX, a meh fighting game. But the most remembered games in the 90s, "the bigger ones", were the SNES fighting games from the early 90s (being all of them, including the console, totally discontinued to be "reprinted" in the early 2000 for the US market. Mega Drive/Genesis also got one, but the same situation of SNES, by 2000).

I do not know if DB is still popular in USA. 

By the way, DB got 2 new series, Super, 10 years ago, and another one now called Daima. Both are considered problematic or even bad by fans. Last one in fact is incredibly stupid and created a huge problem in continuity and canonity inside the series. Far worse than Super did in the day. XD

So it's not your job to write down some of these unwritten rules that you're making for Smash inclusion? I don't recall Nintendo making a bunch of arbitrary, self-defeating rules for it.

Sigh... Take a look on this franchise, we have more than 20 years without a single inclusion (no fighter, no assist trophy, no item, not even a small cameo) of characters whose history didnt started on videogames. Sakurai himself told that this franchise is a "Gaming celebration".

So on my side I have the entire history (+20y and 5 entries) and the creators words. On your side you have your false equivalence that I never took part (I always wanted Crash Bandicoot and Kratos for smash).

You can say whatever you want about "my" rules but until Goku, Shrek or whatever character that didnt started on a videogame show up on the next smash, I wont change my tone. Good? Good.

I wish you a prospere and long life, so you can see the day that I'll eat my own words, if that day will ever come...