Von einem gewissen Punkt an gibt es keine Rückkehr mehr. Dieser Punkt ist zu erreichen.
Beyond a certain point there is no return. This point has to be reached. [Kaiser/Wilkins]
From a certain point on, there is no more turning back. That is the point that must be reached. [Hofmann]
Hofmann makes the second sentence a distinct imperitive, while Kaiser/Wilkins allows for the idea that this point is not stumbled across, that it has to be reached, which might mean it will not come to you.
This is certainly one of the most important and well-known of the aphorisms. It is interesting to think of this as an extension of the previous aphorism; it brings to mind those other dead, not included among the "many," who do not lap at the river of life and are not brought back ... rückläufige Strömung und schwemmt die Toten ins Leben zurück ... the particle rück repeats here and in Rückkehr above. Perhaps they've reached that point.
In the third aphorism, Kafka writes that mankind is not allowed to go back to paradise, kehren sie nicht zurück. This split verb is the same noun as is employed above: Rückkehr.
The point of no return is not passed, but only reached. There's no indication that one goes on past this point, but the point is not reached if one can still go back. From one point of view, this point could be like the South Pole; leaving in any direction one goes North. Leaving this point in any direction would be going back, which would mean one must remain. On the other hand, it might be possible simply to leave that point without going back. Going back is possible up to this point, but not beyond. It may be the moment of unbreakable commitment, but I think the meaning is less occasional and more fundamental to experience than that.
He may be discussing the genesis of the present moment as an irreducible difference from the past. In that case, this would be the moment the new appears, or a sort of natural selection. So the path would be like Herakleitos' river, with an added imperitive and the possibility of not quite managing to reach this becoming.