Realistically, while the prospect of wirelessly-detonated bombs on airplanes is scary to say the least, others say that the chance of it happening are low. They cite in-flight firewalls and the fact that a credit card is required to pay for WiFi as barriers to potentially dangerous behavior. Not to mention the technological barriers already put in place but not shared with the general public. And, additional airport security measures should prevent dangerous materials from making it onto planes in the first place.
While in-flight WiFi seems an easy target for trouble, the reality is that enough security measures seem to exist, preventing any serious risk to its future.