Bittrex showing support for the Segwit2x hard fork. This means you guys can actually keep your BTC on Bittrex, however they are still deciding as to whether they will be opening up markets for B2X trading. As long as you have a BTC balance in your wallet at block 494,784, (can be observed here blockchain.info) you will be credited 1 B2X.
Because Bittrex has yet to confirm opening up a trading market for B2X, my recommendation would be to transfer your BTC balances into Binance for a safer bet instead.
See full details here -
https://twitter.com/BittrexExchange/status/927791499491680256