But the events of the films take place at different times.
In a recent interview, actress Charlize Theron said if viewers will ever see the crossover of the John Wick and the Atomic Blonde. Theron answered the question like this:
Listen, as soon as I get a call, I leave right away. They just need to say where and when I need to be, and I will be there. Keanu is one of the most pleasant people in the world, I adore, respect and admire him. Immensely grateful to fate that managed to star with him in two films. We both seemed to rediscover ourselves in these projects, and “Atomic Blonde” was made under the great influence of “John Wick”. If it turns out to bring these characters together in one film, then I am completely for it.
Both films are connected by the figure of David Litch. It was he who shot the first parts of both John Wick and Atomic Blonde. And he did it successfully – the franchise with Keanu Reeves survived to the fourth part, and “Atomic Blonde” will receive a sequel to Netflix.

A possible problem in creating a crossover is the timeline. The action of “Atomic Blonde” takes place in the late eighties of the last century, and the events of “John Wick” unfold today. Therefore, a common project should be a prequel to one project and a continuation of another. But if someone succeeds in bringing together two proven franchises, the new project will be doomed to success.