I agree with their assessments except for Mewtwo and ROB.
For Mewtwo, their opinions on his chances are based on the incorrect assumption that he was replaced by Lucario. As we all know, he was intended to be in Brawl, but due to the last minute work that Sonic needed to be in the game, he was cut for time constraints. Knowing this, there is NO WAY he isn't in Smash 4. Sakurai will not cut a character he intended to have in Brawl.
As for ROB, I need everyone to state the single example so far of a completely unique character being cut. That's right, there is only one, Mewtwo, due to the aformentioned time constraints surrounding Sonic's inclusion. All other characters who were cut between Melee and Brawl were clones. ROB will be in the game, guaranteed.