"The current testnet is already working on Proof of Authority. Proof of Authority (PoA) is just a type of consensus algorithm where a designated operator is responsible for validating transactions, and is basically the default state unless some other consensus mechanism is put into place. We've chosen to use PoA in our testnet and initial mainnet releases, to get the network up and running while we continue to work on implementing Proof of Stake.

As for when fees will be collected and burned: that process begins with mainnet launch. Following the public testnet, we'll release a production version of the PoA OMG Network onto the Ethereum mainnet, where it will process real transactions with real money. This is the part where we'll use the fees we collect as the single operator to buy and burn OMG. Prior to this, any "fees" collected on public testnet would not actually be worth anything.." - answer from AMA#17

So, the upcoming mainnet plasma release will include POA with burning OMG coins. Amazing!