Random rant about stages for those who don't care can skip:
I wonder if all stages could be included in, there's something like 140 stages in all games + new stages from Ultimate here would mean it'd have 160 stages. That may sound like too much and Sakurai mentioned "we've included many stages" or something along those lines which implies not all of them but hear me out.
Hardcore fans have been counting the stages shown so far from screenshots and the trailers and they've found 85 different stages so far, that's a huge list and it's very probable we haven't seen more. Why stop at 130 if adding 10 more would mean a complete stage list for Ultimate (then again, Smash 4 was only like 5 characters away from having Everyone in the roster and it didn't)
Ultimate is re-using most of its assets from Smash 4, so having all the Smash 4 stages is basically no problem. In the same way, Smash 4 was based off of Brawl which was based off of Melee. So re-using any of those stages from the Gamecube/Wii eras also shouldn't be that hard.
Smash 64 would be an exception, but apparently all Smash 64 stages have been found, this is great since 64 stages only a select few have made it back and we've seen classics like Saffron City finally back. 64 stages IMO are the best since they included the most stage hazards and a reason speculated as to why some 64 stages never made a comeback and it was always the same ones.
The others that would be difficult would be the 3DS exclusive stages but apparently all those are in there as well
Maybe you can argue that some stages are too similar, and that's a legit reason not to include EVERYTHING. But we've already seen stages that are extremely similar and yet both versions appear to be included like Pokemon Stadium 1, Pokemon Stadium 2 and both Animal Crossing stages, so clearly being near identical isn't a problem.
So all in all I'm hoping that it has ALL of the stages. Apparently we're also seeing some Pokeball Pokemon and Assist Trophy characters from previous games that were not in Smash 4, so maybe it'll also include all of those as well?
It'd better