The horizon of beyng is always out there for Heidegger. Even in his final works. In the Summary of a Seminar following the On Time and Being lecture in 1962.

If this is how it is with time—-time being addressed as the transcendental horizon of Being—-then how can the fundamental experience guiding the position of Being and Time be characterized? Is it possible to find the character of withdrawal already in that position? The experience which attempts to find expression for the first time in Being and Time and which in its transcendental manner of question­ing must still in a way speak the language of metaphysics has indeed thought the Being of beings and brought it to a conceptual formula­tion, thus also bringing the truth of beings to view, but in all these manifestations of Being, the truth of Being, its truth as such, has never attained to language, but has remained in oblivion.

P. 29

Beyng withdraws when approached, like the horizon. The truth of beings, another manifestation of beyng, can be viewed, but not attained.

When it is a matter of the question about the meaning of Being, whereas meaning is projected meaning which occurs in and as the under­standing of Being which constitutes the fundamental characteristic of Dasein, then the development of Dasein's horizon of understand­ing is the condition for any development of an ontology which, so it seems, can only be built upon the fundamental ontology of Dasein.

P. 31

Dasein's horizon of understand­ing = meaningfulness of beings = beyng.  ¶ 9:52 AM