Below is an outline of the main events that could unify or divide bitcoin:

• By July 21: SegWit2x software is released and supporters begin using it.
• July 21 to July 31: The community monitors how many miners deploy SegWit2x:

1. If more than 80 percent deploy it consistently, that should signal community-wide adoption of SegWit and the avoidance of a split, at least for now.
2. But if a majority do not deploy, expect anxiety within the community to grow as the focus shifts to the Aug. 1 deadline.

• Aug. 1: UASF is deployed by its supporters, who begin checking if bitcoin transactions are compliant with SegWit.

1. If a majority of miners still do not deploy SegWit2x or otherwise accept SegWit, and if UASF supporters do not back down, then two versions of bitcoin’s blockchain could come into existence: a UASF-backed one where only SegWit transactions are recognized, and another where all trades -- SegWit and non-SegWit -- are recognized.
2. If a split occurs, bitcoin will likely begin existing on both blockchains in parallel, resulting in two versions of the cryptocurrency. Expect traders to quickly re-price the value of both, likely leading to massive volatility.

Source: https://www.bloomberg.com/news/articles/2017-07-10/bitcoin-risks-splintering-as-ivil-war-enters-critical-month