I agree with Agnes and Emma.
I will also add that there is still a lot we do not know about the virus and its-now-more-than-one variant. How often will vaccines be needed going forward? Will ample supply be there? Will those be boosters or entirely different? Just as China (I am almost positive I heard) is dealing with another outbreak, will such occur in other places? While we may (possibly) all get comfortable with what is under control in our home countries, will the same comfort level be there for traveling across the globe to more exotic and remote countries? LOTS of unknowns.
While travel is exhilarating, there is often an equal exhaustion factor. Readers who have been retired for a few years may sometimes look back at 80-hour weeks and 7:00 am meetings wondering how in the world did they do that day after day after day. Younger people, many likely working from home, likely have developed both a comfort (and an off-setting frustration) with the more cocooned lifestyle. Travelers will need to be psyched and energized to go (and my guess is that in 2022 there will be many us ready, but will the world situation really be ready?).
Coming from a household that regularly took 2-3 overseas trips for many years, it will be a while before we consider even one. We need to feel the possibility to safely enjoy a BBQ sandwich on the patio of our favorite casual restaurant first, much less going IN a grocery store. It is hard to even think about flying overseas when we have stopped going to the close-by State park, because we do not feel we can safely socially distance.
I know many will pounce on me and tell me I am limiting myself (or not being open minded), but I have actually called the travel providers that had begun mailing big, expensive catalogs and asked that I be removed from the mailing lists for a year or so (so they may save money and keep the world a bit greener), adding that I will definitely be back in touch (or on-line) when I am ready to be tempted.
But, just like each of us is taking varying levels of precautions right now, each of you will know when the time is right.
I think it will be a slow roll to normal life (including travel) as we once knew it. My guess is 2022 and 2023 with some spurts and setbacks along the way. I also do not expect a lot of bargains. Providers have have a lot of expenses/lost revenue to recoup, and new rules for airline overbooking will likely show up in ticket prices.