For the fans at home the scenario to postpone it for three months or so and then - if the crisis is still not over - think of the option of doing it without audience seems to be the best way: post Eurovision depression shortens, you have a bigger chance of having a "normal" contest, even if in the end you might get a ghost show, but eventually you have your TV-happening, even if perhaps without a party at your home.
For the ones who have tickets, that would be the worst option, because it demands double bookings, rescheduling your timetables and in the end you might have done all for nothing.
For the organization team, that would probably be a better option than to cancel it, because in that case they would loose the most money whereas with a new date and all the people working in place you get at least something out of it. But a double organization would certainly be a huge fuzz, so I think they would prefer a show with no audience.
For the EBU, I'm not sure which would be the best option; perhaps the one were you get a satellite conference with the acts performing at home. But I would not like that one, because it opens the way to heavy cheating #coghautotuneorfullplaybackcough# and all the work of Rotterdam would be completely in vain. (which would probably also be at least partly the case in most of the other scenarios...)