Among the particle theorists and phenomenologists I talked to at lunch at the Perimeter Institute, the probability assigned to this being real was in the 5%-20% range, with older physicists more skeptical.
I like the general philosophy behind Metaculus (that we should all be more public and accountable with our speculation) but I don't think the numbers are currently reliable because posting is open to anyone and there's no money on the line.
I agree, and you provided a link to a nice summary of why.
I do wonder, though, if there's ever been evidence from two independent detectors that ended up being false. That's a significant difference in the present situation.
The 3-sigma that you're quoting may not account for the "look elsewhere" effect: the possibility that a comparable fluctuation might have occurred in any number of other energy levels or other decay channels. It's really hard to correct for that properly, and particle theory has a long history of promising signals melting away with more data. That's why the folks involved are being pretty cautious.
Meanwhile, I'm not sure how well the observed decay mode fits with the most common supersymmetric models: I have the strong impression that it's not one that SUSY phenomenologists were expecting going in.
It's going to be fun to see where this takes us! Maybe a surprise would be the best outcome of all.
Still no liquid betting market though...
http://www.overcomingbias.com/2014/05/how-to-reform-academia...
http://infoproc.blogspot.ca/2006/01/prediction-markets-and-l...