Do you mean you are concerned about merely holding your coins at certain exchanges/wallets? I was under the impression the complications are tied more to payment transactions after 8/1. Poloniex claims to be able to handle the split if you sit tight. However, based on the link below, polo users may LOOSE whatever coins are in open lending accounts at the time of the fork. Who knows what will actually happen, but if you are a polo lender its worth a read.
What other exchanges/wallets are you refering too?
I'm more concerned about the liquidity of the exchanges. If everyone panics and withdraws bitcoin all at the same time, the honest exchanges who actually have the bitcoin will be okay, but others who claim to have bitcoin but in reality don't will have difficulty. We're all made to believe that whatever btcs are reflected in our exchange wallets are there. We shall see.
I was under the impression that the bitcoin people deposit are actually there. But I just found out about the "open.btc" on the bitshares network. They apparently peg the value of a btc to "open.btc", which is what you own... not actual btc. Then I read that all exchanges do this. So when you deposit btc to poloniex, you actually own poloniex.btc or whatever they call it.
I didn't get far enough to understand why they do this, but it is an issue I was not aware of until just recently. Not sure how comfortable I am with that. But I only keep hot currency there anyway. 80% of my crypto is in cold or mobile storage.