@led-naruto
Nice,you understand the first part.
As for Link,supposingly that they take his Skyward Sword incarnation,what`s the difference between this incarnation and the OoT incarnation

Is there some differences between the two in term of their ways to use their attacks or items

In Brawl,Link was based on his Twilight Princess and that changed his boomerang quite a bit,so yeah it did make a bit of a difference in gameplay.I`ll admit i didn`t played Skyward Sword and i have no plan right now,but if Link in that game didn`t had any signifiant changes to the ways he used his trademark items then the change probably wont matter because it`ll simply be some skin change that only a few people will even notice.
Now as for Lucario and Ike,it seems that they are people like you who seems obsessed with the idea that just because franchises got new games with new characters means old characters needs to be thrown out.That`s just stupid since it`s ones of the many ways you can piss people off.
If you want some exemple,take SoulCalibur 5.In previous games of that series,people got used to the cast of character.In SoulCalibur 5,many characters were remplaced and it became ones of the critisms on that game,because they tried to remplace characters with other characters.They were people who complained in Brawl by the absence of Mewtwo as well.Marvel vs Capcom 3 had complaints like this at it`s roster because characters from previous were removed.The worse offender was Street Fighter 3.In the original version of it,everyone was taken out for a new cast and the developers had to bring back Ryu and Ken just to adress that but it still pissed fans off,even with the return of Akuma and Chun-li in future versions.
The point is that people are complaining when you take off characters for others.If it`s something like a bunch of clones like Dr.Mario and Pichu,i didn`t saw anyone complaining over them,they weren`t distinct or interesting to play as so of course they deserved to be thrown out.But now you`re talking about throwing out characters that weren`t clones to begin with,that had something going on with them,just to promote the latest games of their series whose characters most will forget by the time the next games after comes out.They are less uniques,less interesting characters to throw out to make room for newcommers,why not cutting them instead

They could easily cut duplicates and some of the joke characters to leave room for newcommers and since Tekken Tag Tournaments 2 has downloadable characters that are first offered as pre-order bonuses,they could easily do the same for third-party characters.
If they`re to remplace characters,they should only remplace characters if the new character make sense.For exemple,removing Zelda for Toon Zelda wouldn`t be such a big deal since it`s still the same character,just in a different-looking style.Sheik is something else through,but she could easily be her own character without the transformation thing.I never played as Zelda anyway.Princess Peach,for exemple,Rosalina could remplace her while offering a Peach alternate so the change could be superficial at best.Same for Metaknight,Galactaknight could remplace him while offering his skin back as an alternate,or Metaknight could simply be kept with Galactaknight as an alternate skin,so since the two characters aren`t that different from each others the change wouldn`t be as impactful as removing Metaknight for,let`s say,Knuckle Joe.
I`ll leave that Brawl data and Pokemons` popularity aside,but removing characters for more recent characters may win people from the more recent games,but it`ll could cause people that are enjoying Smash Bros to leave,and in the larger picture it`s not winning anybody.Brawl didn`t sold tons of copies because of the recent characters and stuffs,but because it was an awesome game with a big cast of reconisable and more obscure characters.