I think Brawl's purpose was to remove Legendaries, so I don't think one will appear again in SSB4.
We don't really have much to go off of for the legendary argument....
'Course not, that's some foolish words right there Trago. There's literally no argument t' back that up what-so-ever. T' avoid any complaints 'bout clones, they replaced Mewtwo with Lucario. Simple as that.
... Perhaps it was also the fact that there wasn't enough time t' develop the forbidden seven, which would further disprove your point.
Mew is a cat. ._.;