clarification on what constitutes to an F1.5 team

the definition as far as I know of an F1.5 team is one that is on the podium for less than 25% of races. So for example will Renault be an F1.5 team next year because it was an F1.5 team this year? and if they get on the podium >25% of the time in 2019 does that mean they will be an F1 team in 2020? or are they considered an F1 team as soon as the >25% podiums is achieved?