The amount in the pinata should probably double every X days. In this situation, if two people know the secret, it is advantageous for one of them to act immediately.
Right now, unikernels aren't in major production use, so there's little to gain by holding on to an exploit (one would assume).
Correct, but there's also very little to gain by developing it in the first place. Right now, the pinata's value is approximately $2500, or less than two straightforward XSS bugs on Google properties, which are waaaay easier to find. There's just not anywhere near the motivation required to get (mostly well-paid) security people on this. It's interesting, but that's about it.
We didn't really expect the money to be the main motivator. Just a hook to draw attention.