"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
WWDC Rumors: Virtualization and Other Hints at WWDC?
Parallels received a lot of attention for releasing their virtualization solution in April. Virtualization allows users to run Windows under Mac OS X without having to reboot. There has been speculation that Apple may enter this market with the feature built into the next version of Mac OS X (Leopard), but no definite information is yet available.
Meanwhile, a purported interview with an Apple employee is making the rounds, discussing what to expect at WWDC. In general, while the information is believable, there is no significant revelations beyond what circulating rumors have been predicting.