Eh... not so good, I think (20% chance, I'll say). Bowser couldn't even make up the difference of 8% going from LFF with Mewtwo and Toad to no LFF at all. Samus seems as strong as ever.

I think MM's hopes have less to do with LFF and more to do with the hardcore fanbase factor / how much of a favorite Samus is. Samus has held up quite well so far, but she also has faced pretty weak characters, and no one with much overlap aside from extremely weak Midna. In the BR she held up very poorly, but that was obviously against a whole other caliber of characters than MM and Yoshi. So next round is more about good old fashioned SFF (except 3-way, and we already know MM will hold up against Yoshi).

I'll optimistically claim MM has a 1 in 3 chance of winning that.
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R.I.P. Robert Jordan, 1948-2007