"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Aside from Signal Issue, Consumer Reports Rates iPhone 4 Highest Amongst All Smartphones
AllThingsD (via LoopInsight) summarizes the report (subscription required).
The [iPhone 4] scored 76 out of 100 points -- two points ahead of its closest rivals, the iPhone 3Gs and the HTC Evo 4G.
The product evaluation agency rated the iPhone 4 "Excellent" in its display, navigation, Web browsing, multimedia and battery life categories, "Very Good" in phoning and messaging and "Good" in voice quality.