Any B2X that exists on any exchange prior to the fork is a way of telling that these exchanges believe in the project and it's potential and in order for them to give their traders a head start they created a virtual virtual currency named it B2X  and enabled only exchanges to BTC and some other altcoins. But you cannot transfer your coins outside that exchange platform until the fork takes place and there is a BlockChain for B2X to actually start building on top of. Long story short if you want to buy the B2X now that you think you will get when the fork happens, go ahead at your own risk, otherwise I would wait until the fork takes place here in a couple of hours. Cheers and don't forget to HODL!