That's the issue people have with Segwit. Once you go Segwit, you can't go back because all transactions done under Segwit (and all blocks/forks after Segwit) will become invalid without the
centralized Segwit nodes validating the transaction. This will forever give the validating Segwit nodes power over Bitcoin's destiny. And it'll only take less than 6 years for a wallet developer (ie: Bitcoin Core) to centralize and completely usurp Satoshi's vision.
Reading the many responses on this topic is making me more confused. I am just an ordinary guy holding a little amount of Bitcoin and I am essentially on the dark as to what can happen this coming August 1. Will there really be a fork or a split in Bitcoin or is this fork just a negligible decision of a group of miners which will eventually not affect the whole Bitcoin?
I have been reading about Bitcoin Cash too and I understand that it can be a new altcoin bearing the name Bitcoin but this will not have any major effect on the real Bitcoin. Now, if I have some Bitcoin left in a well-known exchange will it mean that my coin is automatically lost or it depends on how that exchange will protect their members' funds?
Things are really mired in the mud right now as we are all just expressing my ideas and opinions here and it seems that nobody can speak with certainty on what can be. Must be another manifestation on Bitcoin's decentralized set-up.