Whilst reality-based rather than in a storyline, sadly Professional Wrestlers seem to have very short life spans. Prior to drug testing (which was implemented after one such death), wrestling has had a number of high-profile deaths that seem to come out of nowhere, most notably Chris Benoit and Eddie Guerrero. Certainly fans are now conditioned to expect any wrestler to die at any time.
You also never know when an accident may happen, such as the one that claimed the life of Owen Hart.
And of course accidents can occur outside the ring, as what had happened to Randy Savage.