Before heading towards the hard fork details , lets understand some of the basics :
Hard Fork : A permanent divergence in the block chain, commonly occurs when non-upgraded nodes can’t validate blocks created by upgraded nodes that follow newer consensus rules.
This should be not mixed with the soft fork/software fork/git fork :
Fork (a regular fork where all nodes follow the same consensus rules, so the fork is resolved once one chain has more proof of work than another)
Soft fork : a temporary divergence in the block chain caused by non-upgraded nodes not following new consensus rules
Software fork : when one or more developers permanently develops a codebase separately from other developers
1 . In the Bitcoin Improvement Proposal (BIP) 148 , Bitcoin would be going through the soft fork on August 1 , so hard fork would be available after 12 hours of Segwit.
In this BIP 148 ,high possibility would be split of the bitcoin blockkchain into two as happened earlier in case of ETH and ETC, one would be of segwit and other is without it.
There are risk involved in this process as the orphaned blocks and missing transaction would get increase.
It would be highly advisable not to do any trade on the bitcoins till Aug 3 , once hard forking gets streamline then approximate 95 % of backing of miners for this hard fork.
There might be a case arises where hard fork may not be a mandatory as currently BIP 91 is getting 62 % miners support, so if it attains the support of 80% before Aug 1 , then hard fork may be skipped and smooth migration to segwit would be possible.
BIP 91 seems to be saviour for the chain split between Segwit2x and BIP148 .
In the days of Aug 1 - 3 , you might see your bitcoins getting to 0 and if you have kept in a wallet , then it would depend upon the wallet which chain , it would be accepting. Its better to kept hold on your bitcoins and avoid any transactions meanwhile.
After this Segwit2x , exchanges would definitely provide the support of two split chains and would not be creating any issue regarding your holdings of the bitcoins.
Hopefully this chain split would get complete seamlessly and BIP 148 and Segwit2x are made fully compatible.