Well, this is a fan-made fake and it’s looking like there’s another “Amon unmasked” image floating around the fandom (AVOID THE “AMON” TAG, TUMBLRERS!), but it just seems unlikely at this point.
First, it would require that everything we know about Amon up to now be a very complex lie. From his backstory to his apparent age to his voice (because Tenzin is both the youngest member of the family and would likely recognize his brother’s voice).
Mostly, I don’t want it to be Bumi because I don’t think this series is nearly as interested in connecting itself to A:TLA as we, the fandom, want it to be.
I’m not sure we know who would knock-up Toph or if we’ll ever learn if Ty Lee had anything to do with Chi-Blockers. I’m starting to think that the world-building on Korra is – more often than not – actually just world-building for this one series.
My favorite “Who Is Amon" theories currently running are "Bolin and Mako’s lost brother” and “YaKone’s Son.”
-Da7e-