I'm not a physician, not a virologist, and not an immunologist (I am a researcher though). with this caveat in mind, I can still let you know my thoughts:

I did not see referral to an option:

A person who was vaccinated with a spike of some variants, is relatively protected against severe disease for various mutations not so distant from the one he was vaccinated for. At this stage, if he is infected with the new variant, even though the antibodies will identify only some epitop, and it will take more time for the B/T cells to generate new antibodies, the remnants of the new variant will be identified and learned by the immune system, and thus the person is likely to develop immunity also to the new variant.

There is also another point - when we see the changes in various variants, we see that almost all of them have already appeared in former variant, and mainly, it is a differeny combination of them. This seems to me as quite optimistic, because it suggests, that beyond some finite changes that are more likely to occur, other changes are less likely to occur.

an interesting link - though.