I’m not as smart as Scott but for me it’s more like 10% -> 20%. Do we have a prediction market for this?

It seems highly irrational to bet that your evaluation is more likely than Aaronson's.

Predictions markets are terrible mechanisms for this, because they require imposing an arbitrary time limit at which point the prediction will pay out. IOW, even if you religiously believed P=NP, but you think it would take at least two years to prove it, you would vote against the prediction if the deadline were one year.