"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Sketchy Report Claims No New iPad Air in 2015, One Last iPad Mini
While the iPad Air 2 may not see a refresh, the iPad mini 4 and iPad Pro will see introductions. Liaoxian Li, investment advisor at Fubon Hardware, tells Economic Daily News that Apple may want the attention on the new iPad Pro and thus will let its main assembly plant for iPads, Foxconn, focus on the Pro to maximize deployment capacity. Li believes a new iPad Air might not be released until 2016. Economic Daily News has a mixed track record on rumors and the accuracy of this particular analyst isn't known.
Additionally, the report claims that the new iPad mini might be the last one as the Apple wants to focus on the two larger iPads in the future. Many people were disappointed with the iPad mini update in 2014, which essentially added Touch ID to the existing iPad mini 2. The next iPad mini will likely be more of an upgrade, with a rumored rear shell featuring iPad Air 2 design elements already making the rounds.
While it's possible Apple won't upgrade the iPad Air 2 this year, the company has been constraining supplies of the iPad Air to third-party retailers, suggesting the iPad Air 2 would become the lower-cost option as an iPad Air 3 slots into Apple's tablet lineup. However, it's possible Apple introduces an iPad Air 3 with minimal additions, as it did with the iPad mini 3.