Chances of those scenarios coming true are slim to none, historically speaking. Reality is that conventions will resume when everyone involved is okay with the risks associated with a convention. A more succinct way to put it is when the panic dies down in the general populace and cooler heads prevail, conventions will resume with or without a vaccine or 100% effective treatment. Considering the state where Blizzcon is located, it's not surprising that a physical convention is being canceled due to various external pressures... however the state/city data offered by their local governments and the typical attendee demographic of Blizzcon, there's no real risk not to have a convention right now beyond what they would normally experience. It's likely Blizz covering their butts legally until the panic dies down with a dash of virtue signaling to taste, although I can sympathize with covering their butts legally considering how insane people are getting over the entire scenario.