Of course it's always good to plan for worst case scenarios, but if we keep up social distancing, then we might not even have an uncontrollable second wave. The countries that are reopening certainly haven't reported any explosion in cases thus far (I know everyone's saying that Germany had a second wave, but their R0 number is still only at 0.74; it needs to be above 1 for a second wave to occur).
I'll use the Spanish Flu pandemic as a historical example. During the first wave, it was not as bad as expected. Due to this (and also partially due to the war effort at the time), no social distancing was applied at all, and the second wave was devastating. After the war ended, when the third wave came, social distancing was applied, so the third wave was nowhere near as bad as the earlier two and a fourth wave didn't happen.
If you want a historical example of a recession, then the Great Depression in the 1930s was very bad and quite drawn out, but nothing in the way of financial support was applied whatsoever, so it went badly. But look at the amount of financial support governments across the world are applying trying to prevent a bad economic crash now. If more is needed eventually, then I'm sure the governments will offer it; as Rishi Sunak said when the government first announced its initial financial measures, they will do "whatever it takes".
I'm not trying to pretend that everything will be fine once things reopen, as I know that won't be the case. It won't be like flicking on a light switch; it will be a more gradual recovery. However, I think there could potentially be a v-shaped recovery once things reopen; the amount of people I've seen saying that they want to go to a restaurant or go on a foreign holiday when they're allowed to suggest that there's quite a bit of pent up demand building while we're locked down.
So what I'm basically trying to say is; while expecting things to be an instant recovery would be unrealistic, I also don't think it will be as apocalyptic and morbid as some are suggesting, either. The world will still go round, and businesses will still operate and receive income.
I too am very worried; very, very worried in fact. Perhaps the most scared I've ever been about the future. But if you look, I think there's reason to believe that there will be light at the end of the tunnel fairly soon, personally.
With regard to Merlin, it's worth remembering that they also have a hugely expansive foreign portfolio to fall back on. I know many of their attractions in mainland Europe are reopening within the next month, and I think some of their attractions in Asia are open now.