On 11 of Jan this year and there would be a snapshot of all ethereum wallet and you would be given 3:1 of whatever ETH you have in your wallet has ethereum classic vision which I heard Is the future of all cryptocurrency
Not only on January 11, there are 2 more ETH events to look out. January 12 is the hard fork for Ethereum Nowa and January 14-18 is the hard fork for Ethereum Constantinople. The hard fork for Ethereum Constantinople is believed to the major one so if you plan to sell your ETH right after the snap shot at January 11, try to hold on to it a little bit longer as a major one is just 8 days away from the first hard fork.