ABAP will always be used as long as the SAP versions running ABAP continue to work and continue to receive support.
But if you ask me, contrary to different answers, that ABAP is the future or growing? no, it is evolving, it’s getting new features every release and trying to catch up with the new paradigms of newer languages.
But, beside the businesses that have already got a SAP, the question of whether ABAP will become obsolete or not, relies on newer customers. The ERP market is additional sturdy currently than it was ten years were gone. New ideas exist now, like advanced algorithms, machine learning, etc.
And ABAP may be a very powerful language for business running, but not so powerful/quite verbose for more advanced systems.But i think that ABAP combined with UI5 and simple to integrate with different languages, may give SAP the leverage it needs to win the new companies in the market. SAP (and ABAP) should evolve to adapt to the new reality