Wait for the September Apple Event
Another reason to wait for the new Apple TV is simply that it is almost here. Apple is planning to hold an event on September 12th according to multiple sources. We expect to see the iPhone 8, iPhone 7s, Apple Watch 3 and the new Apple TV at this event.
Apple didn't send out the invites for the event yet, but enough sources are coming together to say this is the date for the event that it makes sense to wait. This is roughly two weeks away, and even if your current Apple TV is broken or you have cash burning a hole in your pocket -- you should wait for this event.
Once the event arrives, the new Apple TV release date is likely to come with in 2 to 3 weeks, which means a little more waiting, but the Apple TV isn't cheap and it's worth waiting to find out what the new one is about before you upgrade.