First off I do agree with the theory that she's probably only carrying the code name for the start of the movie, maybe she dies, Bond comes back into play or whatever happens he ends up with the 007 title at the end again.
Still the whole ploy to use a black female as 007 no matter if it's for a scene or two, or half the movie is just such a lame move by the studio. They're doing it so they can say things like "anyone can be a badass agent" and "a woman can kick ass too" and I'm not saying these are wrong, but they're using the James Bond franchise to do this in. I think Lynch is a good actress and she probably could be a badass agent but it's like if you had 100% faith in this you would put out a movie called "Jane Kickass" or whatever, make a new original female character and make a movie like that. Using one of the most known IPs in movie history to do this is kinda like taking a dive in the deep side of the pool but you're wearing a life jacket. Then again look at a movie like Lucy starring Scarlett Johanson, pretty much nobody went to see that.
Then you got the endless debate that James Bond has no place in the world in 2019, a typical man's man (who is also white) who gets every woman to sleep with him and saves the world. For me personally I don't care going into a movie what race or gender the main character is, but I do believe in keeping it somewhat consistent with what the character always was.