No, ABAP will never have the NOT operator.
Before 7.4 we had to do this, for example:
IF a = abap_false. b = abap_true. ELSE. b = abap_false. ENDIF.
Then came 7.4 and we were able to start improvising:
b = COND #( WHEN a = abap_false THEN abap_true ELSE abap_false ).
But even this is too far fetched for such a simple need.
Nevertheless, the boolean function XSDBOOL can help us get a little closer to the ideal NOT:
b = XSDBOOL( a = abap_false ).
This is the best I could find. If you know of a better way, please let me know.
Greetings from Abapinho.