I was wrestling with the same question buying one as a gift for a friend, so I'll give my hesitations and conclusions:
1. Will there be a new Apple TV before the end of the year?
Almost certainly not. An Apple CEO recently said the holiday lineup is set. I wouldn't be surprised if we see a new one along with the new Apple tablet, but you're safe from immediate obsolescence.
Also, if Apple continues their tradition, you'll probably receive some sort of software update to pick up several of the new features, so you're probably good in the future for things like an App Store or iTunes extras.
2. What about waiting for the new remote?
I called 1.800.My.Apple twice, and both times they said they're not even sure if they're shipping the new remote with the Apple TV. What they ended up telling me is that if it made the difference between buying now and waiting, they would mark a note on my account, and send me the new remote if it indeed shipped with the Apple TV soon. If you call them before you buy and buy now, there's a chance they may cut the same deal for you (giving you two remotes instead of one!).
3. Is it a good time to buy in terms of price?
I thought it was worth it back when I paid $220 for the 40 GB hard drive! Now you get a 160 GB drive for the same price! This one's a no-brainer.
My advice? Go for it now! You'll at the very least get a few months of enjoyment with the latest and greatest hardware and if new hardware comes out (which is still a question) and it's all that compelling and different, you can always sell your Apple TV and use the funds toward the new one's purchase price.
I don't know how used generation old Apple TVs will fare on EBay, but historically Apple products hold their value pretty well, so you can consider an immediate purchase a rental, which would be totally worth it, IMO.
By the way, I just checked EBay, and I noticed an "open box" 40 GB model still fetches $170+.