GPS and Bluetooth won't happen because
- They waste a hell of a lot of battery life
- They aren't needed in the iPod
- They decrease differences between the iPod touch/iPhone
If you want a touch, get it now, the software is the killer thing about it, and that's where most of the additional functionality is going to come from for a few years. Many hardware updates won't happen, but the software will be updated for presumably years.
However, if you must wait for a hardware update, expect one mid-to-late September or October. Again though, minor updates.
Ace