It depends on the degree those more susceptible to this virus are vaccinated: if there's ... say ... 20% of those 65+ not vaccinated, then they may face a new crisis with Delta while the other 80% are much more safeguarded.
Just because the percentage of those vaccinated is high, doesn't necessarily mean that those more susceptible are all (or close to) vaccinated.
For example, here in Portugal, this is the current distribution of the vaccines (click to enlarge):
View attachment 48160
As can be seen, 94%+ of those aged 65 to 79 are fully vaccinated and 96% of those aged 80+ are also fully vaccinated, which means
a VERY LARGE percentage of those most susceptible and now protected against more severe effects from this virus. Dunno if those that aren't vaccinated are due to other medical conditions that prevent them or if it's their refusal to be vaccinated: no data available on that.
Portugal is currently experiencing a 4th wave with this Delta variant but our R number has FINALLY gone below 1 (was @ 1.19 just 3 weeks ago). We were having an average of around 3.4K new daily cases (the equivalent of 108K when accounting for the population difference VS USA) over a 7 day period but it is now dropping and is currently around 2.55K. Portugal has already announced restrictions lifting based on vaccination goals.
If your location has a similar age distribution of vaccines as Portugal, then you are most likely correct and the odds of a new lockdown being required are very slim, assuming ofc no "more troublesome variants" come our way.