It is hard to tell. If you want one now, I would wait the 9 days until the Sept 10th announcement. Yes there will be much more announced in the rest of the year, but its $99. Waiting 9 days to make an investment is fine, but more than month or two and you are really messing out.
I honestly do not see what they can add but minor stuff like AC. It is all ready almost all cloud based. I see the current generation supporting everything they plan for Apple TV until the actually TV set comes along. The ac is a fine upgrade if you need it, but there is nothing on the rumor front and for $100 I would not give up more than a month or two just to have access to it.