As much as I'm going to miss Mewtwo I think I'll be happy with Lucario who happens to not be a clone of Mewtwo. They really only have two attacks in common so being a clone isn't really a good theory. Besides if they were going to get rid of Mewtwo then why put a clone in his place? (unless they thought it was a good idea like toon link (which is a horrible idea)) Anyways after actually looking at the movesets and how the two characters play you will realize that there is no possible way that they are clones.
I’ll post what I posted in the other topic here as well:
They share very similar hit boxes
Up smash and side smash are basically the same
lucario's >b works in the SAME way that Mewtwo's did (No it's not comparable with Samus')
lucario's ^b is a visible version of Mewtwo's
lucario's jump and falling animation is the same as Mewtwo's
lucario's tilts are also very similar to Mewtwo's
Not clones but close enough to be called Luigified
Mewtwo is completely gone from Brawl.
I suggest trying to do some research of your own.