The 4th Generation iPod Touch was released on September 1st, 2010, then taking two years before the 5th gen. debuted on October 11th, 2013. Then, for about three years there was no word about an iPod Touch, where the 6th gen. was released on
July 15th, 2015. Therefore, it is reasonable to speculate that the iPod Touch will be released either later this year or mid next year.
The next generation iPod Touch may see Touch ID included. The next generation will include better processors. It would also include improved camera, which some say would be similar to the iPhone 7 Plus.
Until the actual release, we can only sit back, speculate, and wait. Remember, this iPod may debut along the iPhone 8.