Steam announced the impending integration with Bitcoin, they announced it earlier today after it was discovered in a Beta client release. Soon after they released an announcement and tweeted in from the @SteamDB account.
This comes in good time, users have been expecting Bitcoin integration for some time now. Bitcoin payments will be integrated throughout the entire Steam platform. This means you will be able to buy games directly from them using Bitcoin.
Bitpay will be enabling the transaction, Bitpay transact between Bitcoin and the local currency. Users will pay Bitcoin which will be converted on the spot to the local currency and sent to Steam. Valve has no intentions to hold or receive Bitcoin right now.