We are hypothesising about a scenario where hospitals become overwhelmed again which is the only scenario that justifies any lockdown, which given the current trajectory will only happen if the vaccine effectiveness is severely challenged by this new variant.
It also needs to be more transmissible than Delta otherwise delta will remain dominant. And it also needs to be as severe or more than the previous strains to cause the same level or more hospitalisations.
All of that is possible but no one knows at this stage, not even the scientists or politicians, until it’s been examined. It could literally turn out to be a nothing variant like a few of them have before for all we know