Is there any danger / risk having my bitcoins at poloniex after 1. August ? Also will my current Bitcoins remain Bitcoins (and not BCCs or a mix) at poloniex and bittrex after 1. August ? Cant find the answer anywhere !

Ya it is danger to keep your coins in Poloniex because what will be the result no one knows so it is much better to keep your coins in Desktop wallet or hardware wallet.