Of course it is possible that some deaths will come later, such as people who missed their medical checkups, have a condition that could have been cured a few months ago but is fatal now, and are still alive at the moment. I don't really think this is a large part of population.
I also suspect that if you do the simple calculation "excess mortality minus confirmed COVID deaths", this will be an overestimate, because many COVID deaths are misclassified as something else, e.g. pneumonia. And all those misclassified excess deaths would then appear as "victims of lockdown".