According to F4WOnline.com, NXT Takeover Events moving forward will permanently be moved up one hour to a 7PM ET start time on Saturday nights with a Pre Show starting at 6 30PM ET. Previous NXT TakeOver Events such as the recently completed NXT TakeOver: Chicago had a start time of 8PM ET with a Pre Show that started at 7 30PM ET. 
There is no word yet on if the change will be in place for NXT TakeOver: Brooklyn IV during SummerSlam weekend in August but it is definitely the case for NXT TakeOver: Los Angeles in November during Survivor Series weekend. It was discussed that the idea is that the shows will not be longer but that is probably what will end up happening. The current directive is that the all NXT TakeOver Events moving forward will be less than 3 hours in length for the main show.
Source: F4WOnline.com