Ethereum hard fork

Could somebody explain me about hardfork?

I bought 500 DAO tokens on crowdsale for 7,5 ETH, there was the last day of crowdsale. After hacking TheDAO I sent my DAO tokens (on 17th June) to Poloniex and sold them there. 

Now, I have a question.

Can I expect to return 2,5 ETH (or less) to my ethereum wallet? Or I can already forget about them?

Thanks for you attention.