"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Total iPod Touch Sales Estimated at Over 45 Million

According to market research firm Asymco, Apple's iPod touch has been estimated to have sold more than 45 million units over its lifetime, or nearly 38% of the 120 million iOS devices cited by Apple CEO Steve Jobs at the company's media event last week as having been sold.
We know that there were 59.6 million iPhones sold through June (from SEC filings)
We also know that 3.2 million iPads were sold.
If we assume about 8 million iPhones and 4 million iPads were sold during August and July, the total number of iPod touch sold is 45.2 million.
The calculations are merely rough guides, as they are based partly on estimates and partly on vague claims from Apple and Jobs of milestones shared as "over X number devices" rather than hard data, but they do provide an interesting perspective on the relative performance of Apple's iOS devices. Apple does not officially break out iPod touch sales in its financial reports, choosing instead to lump it in with all other iPod models in a single line item. Jobs did note at last week's media event, however, the the iPod touch has overtaken the iPod nano as the company's best-selling iPod device.