OnePlus has been teasing the 6T for weeks, and we were supposed to learn all the details on October 30th. Well, now you won't have to wait quite as long. OnePlus has moved the date up a day in response to Apple's announcement of an unusual second fall event on the 30th.
According to OnePlus CEO Pete Lau, the company carefully considered how to proceed after Apple announced its event. Although, I don't think OP had to ponder for very long. Just a day later, and the OnePlus 6T unveiling has moved from the 30th to the 29th. As far as OnePlus has come, it's still bound to garner less attention than Apple. The last-minute change is less damaging than being swallowed up in the Apple news cycle.
So, OnePlus will be the big technology news of October 29th, and it'll have a day in the spotlight before Apple swoops in. The event will still start at 11AM EDT, so update your calendars as necessary.