Why? This demand contraction is sector specific and largely due to a temporary shock. Tons of companies are doing fine, and local, state, and fed have programs to stop-gap a lot of these issues (interest-free loans, tax cuts, loan freezes, QE, etc). Why do you think these aren't enough for the next 2 months or so?

I think it will really depend on how long the hit lasts and, at least in the US, how much the government does to help keep businesses afloat in the meantime. If most businesses can come out of this in bad shape but intact, then things might pick up quickly. However I think that depends almost entirely on how well "social distancing" etc reduces the spread of the virus. If it works well and reduces outbreaks to a minimum, it's in the realm of "manageable" economically, though even then, as you point out, it's a "not in our lifetime" event. If the virus isn't well contained though, then we're probably looking at the timeframe for a vaccine as the minimum time before things can start their long trail upwards again.