Well its been revealed that Mega Gallade get Inner Focus which is nice to stop flinching (looking at you mega kang/jirachi) which is nice. It still being Fighting/Psychic? Not really surprised. Primal Rayqyaza is likely going to happen anyway. So I'm not surprised if he gets it either.
I feel like Inner Focus is a wasted ability on it. Justified is good enough imo.
If it got a reasonable speed boost with it's Mega form, things that rely on Flinching moves(not Fake Out), it would be completely useless.
Mega Kanga is not relateable in this situation(unless you don't follow Smogon rules). Then there's Jirachi who probably won't enjoy a Knock Off(does Gallade learn it?). Togekiss can probably handle it, unless Ice/Thunder Punch does alot.
Fake Out users I know of: Hitmontop, Ambibom, uhhh... None of those don't like their STABS.
Since I don't know stat changes, it's all speculation.
Mega Medicham will be the better Psychic/Fighting Mega imo due to Huge Power.
It will probably be around Middle UU in my guess.