As you say, no one can predict. What I would say is that the briefings to the press are very negative about lockdown ending anytime soon and international summer travel. Even Mr Johnson, notorious for overoptimism, is reigning in his exuberance.
Last November I booked Santorini to avoid a voucher expiring, we are due to travel at the end of June. I thought the chance of going was 80/20, now I think its much more like 80% chance of not happening. I don’t see travel being ‘normal’ this summer and wont be booking anything else.
Even Spain who, as we are always told, need our tourist money to ensure their very survival have said that they will not be opening borders until 80% of their population is vaccinated. As of 2 days ago El Pas report that just under 100,000 are vaccinated. Spain has a population of 47 million, so its going to be a while before travel gets back to any kind of normal. In all likelihood Summer 2021 will be as bad, if not worse, for the industry than 2020 was.