I think it will depend on how things develop/how well the vaccines stand up to new variants etc. as well as how long vaccine induced immunity lasts (could last 6 months, could last a lifetime!)
My instinct/hope(!) is that once we've fully vaccinated everyone once or twice there should be low enough levels of virus circulating and enough background immunity in the population that we can get away with only vaccinating higher risk groups alongside flu annually with maybe boosters for all every 5 years or something similar.
Also these are first generation vaccines, they may well be able to improve on them yet.