There are over 4000 different mutations of the SARS-CoV-2 virus. Mutations are nothing new. The issue at the moment is that transmission is high so a vaccine resistant (which none of these mutations are) "could" come in and take advantage of the high transmission rate to spread quickly.
Once transmission is reduced, which would happen in the summer months with or without a vaccine, a new vaccine resistant mutation could not come in and spread quickly. This gives time for vaccines to be tweaked to combat the new variant.
Once a large section of the population is vaccinated then transmission will be reduced and again a new variation could not come in and spread quickly, again giving the vaccine time to be tweaked.
The SARS-Cov-2 virus is going nowhere, and will be come endemic in the human population. It will continue to kill people for decades to come, and people will be required to be vaccinated probably every year like flu.
We will just get on with life.
But as for travel, I think this summer will happen. Just probably not until the summer.