Yeah, I'm sure that most of us thought of stage hazard and items dropping panel on 5th controller for someone who would got eliminated. (being specific last place player)
I support that but that would lead me to one technical issues. If they go with 5 players, then it wouldn't work because people would have to swap the controller between last place and GamePad controller. I seriously doubt that we would get 5 players battle tho, so I'm fine with 4 players as usual. It would be interesting if it happens tho.
I think they should revamp Luigi to honor Luigi's Mansion series, and change his logo to the logo that was shown at NintendoLand. Also they should remove few luigication characters, and revamp one or two luigication characters, such as Wolf and Lucas. I know Lucas have a lot of potential with his final smash and few moves but they took cheap way out. Same for Wolf, he should able to drive in Wolfen, not a tank.
It would be safe guess that we are getting 42-49 characeter slots. I highly prefer to see 49 character slots and 1 random, but I will have low exception from SSB4 this time due to interview from Nintendo Power. It sound like they are going to change it to make a impact on the community. It's possible that they might try to make it more newbie friendly, since they don't want catering the hardcore. Unless they decided to give all characters 4 more moves with one new button or something.
Honestly, I think that they still have plenty characters to pick for next two sequels, (SSB4 and SSB%.) Afterward, I would see that they might have issues to pick better characters unless they create new IP by then. Takamaru, Little Mac, Golden Sun, Animal Crossing, Bowser Jr, King K. Rool, etc.