They'll keep it unless enough pressure is brought to bare on them - so unless US authorities heavy them, someone sues them, or there's such a big public outcry, they will keep our BTG. It's nothing personal guys, it's just that they want that money for themselves.

Legally, they haven't got a leg to stand on, but hey, what do minor details like, "unconscionable conduct", or "unjust enrichment", or "holding funds as a fiduciary" matter?

Easy solution - hold Bitcoin on Bittrex not Poloniex if you must hold on an exchange - they've never pulled a fast one with any forks I can remember.