First off, anyone can make a leak. Just because it is from a website doesn't make it any more credible than it was before. Here's the leak if you aren't familiar:
http://gematsu.com/2014/04/rumor-shulk-palutena-set-super-smash-bros . So many of the things they predicted were extremely obvious.
Mega Man and Pac-man were obvious. I don't know how you're going to argue against that, but they are the most obvious third parties (to me).
Pokemon from X and Y is also really obvious. No matter what, GameFreak is going to put a pokemon from their newest game in. In Melee it was Pichu, in Brawl it was Lucario, and now it's Greninja.
Little Mac is one of the most requested characters from America. He was pretty obvious to rank up to playable character. (He is
the Nintendo fighter. That's everything Punch Out is about, fighting. How could you not include him?)
Miis. Miis are everywhere today. If you didn't think that Miis were going to be in Smash Bros, what rock were you living under? People expected Miis for Brawl, where they didn't get in. Now was the next best time to reveal them.
Palutena is next. Sakurai loves his own series. With Kid Icarus just getting another game and how well it did, it's pretty obvious they were going to add a second Kid Icarus rep. Magnus wouldn't work, too irrelevant. So Palutena was the next best choice. Don't even bring up any of the villains, because, dare I say it, they're too big. Not like Ridley, though. Those things are colossal. Like mountain size.
As for Chrom, Awakening was guaranteed a rep. I haven't played it, but it was pretty obvious to me that Sakurai wouldn't do 3 blue-haired swordsmen.
[EDIT: MALE SWORDSMEN. I don't want to get Lucina thrown at me.]
Villager is obvious because Animal Crossing is a huge selling series. It's amazing it hasn't been repped before. They needed a rep for it. Instead of the peaceful villager, we got the god of death. I'm okay with that.
For Shulk and Chorus Men, I haven't played their games, but with Shulk getting a Wii U sequel and the series having good reception, I feel he held a decent chance.
Now for the one not many people were expecting, Wii Fit Trainer. Actually, when you look at it, she was really likely. Wii Fit U is a system seller. Maybe not to you, but to fitness centers and nursing homes (I've seen it happen). Wii Fit U is the reason these places upgraded from Wiis to Wii Us. All of the new features in Wii Fit U is a great offer for these places. I guess this is Nintendo's way of saying thanks to the Trainer. Also she's athletic, like one of the most athletic Nintendo characters ever (because she teaches it).
These are just my views, but they're off topic. It'd be preferred (by everyone) that if you have something to say on the matter, you'd PM and not reply in the thread.