All this is quite confusing. Someone is saying that it is still not 100% sure that the SegWit2x will be activated or not. And someone is saying that a split is still going to happen, with Jihan Wu & Co. pushing hard with Bitcoin Cash (BCC). Anyway, as per my understanding, there will be no chain split now. The BCC will be an altcoin rather than a split version of the BTC.
What you don't understand is that anyone could cause a chain split at any time.
BIP91 has been locked in. SegWit will be activated. We'll find out in three months whether miners follow through on their agreement to fork to a 2MB base block size. At that point there will be a chain split.
As for Bitcoin Cash, that's unrelated to BIP91 or what the vast majority of miners are supporting. BITMAIN-operated pools (pools led by Jihan Wu) are supporting BIP91
as a compromise, but they would ideally like Bitcoin Cash to succeed, as Bitcoin Cash is similar to Bitcoin Unlimited (block size increases).
You could argue that Bitcoin Cash is an altcoin, or you could argue that it's a modified version of Bitcoin. Either way, it will happen on August 1st and you will own some of it.