There is some confusion regarding the changing of bitcoin from the current blockchain. There are differences between a hard fork, and a soft fork, and this upcoming change is certainly only a soft fork. But markets may panic and so some platforms and exchanges are freezing bitcoin assets temporarily during the decision.
(A wise precaution)
Soft Fork – A soft fork is a change to the bitcoin protocol where some previously valid blocks/transactions are made invalid, and the rest of the previously valid blocks/transactions are kept valid. Old nodes will still recognize the new blocks as valid. Soft forks don’t require any nodes to upgrade since all blocks with the new soft-forked rules also follow the old rules, therefore old clients accept them. This kind of fork requires only a majority of the miners to upgrade in order to enforce the new rules. ~ Excerpted from here.
Under Bitcoin Improvement Proposal (BIP) 148, Bitcoin will be undergoing a user activated soft fork on August 1, 2017.
Coinbase has more to say about it here.
And Bitcoin as well here.
One of the biggest changes seems to be who will be supporting the new version – in fact so far Slush’s pool and Coinbase are both opting to not.
The anticipated dip in value will almost certainly be temporary. We’ll see another rush of miners and would be miners trying to get into position with the new blockchains pretty quickly.
“We want to let you know, that we currently have no plans to support the emerging Bitcoin hard fork called Bitcoin Cash (BCC) scheduled for the Aug. 1st, 12:20 UTC. As for now, we do not see a real demand from miners and the costs of creating and maintaining separate Bitcoin Cash infrastructure would be too high.” ~ Slush’s Pool