Keaton will be treated as A-level canon. Should already be doing it since the only actor that played it more than once and the original. The neon movies are now a branching alternate timeline i guess. The Muschiettis claim that everything filmed still exists and they won't "forget" anything, not sure if they're going to distribute official terms or designations during their marketing campaign. at&t seem to be pushing the whole Multiverse thing pretty hard. Does that mean Clooney and Kilmer are now in different worlds to explain why they look different? I don't know.
I'm aware of 90% of the newspaper props and wanted poster being mostly gibberish, since they never expected anyone to ever look at it that closely. Of course those random small props offer contradictions. But my main point is references to pop culture in our world, spoken as lines of dialogue in the film would be "a-level" canon that can't be swept under the rug like everything else. And there are major visual props that have large print, knowing that the audience could spot it. (the date Shreck's company was founded on side of a loading truck) Shreck seems older than the other characters, only slightly younger than Grissom. And the birth certificate seems like thought was put into it, mores so than the newspapers. Even though chose not to show it, it's still production made and i'd put it above the average newspaper prop. The villains whole plot and motivation revolves from birth certificate research scene and his mysterious list.
Terrible expanded universe comics never make any sense. Has nothing to do with the actual movie.
The 1989 movie takes place in an alternate 1979, based on the American Express Card advertisement reference and dates on props. The sequel, Batman Returns can take place no further back than 1983, based on the Love Connection reference and Penguin's birth certificate prop. It's interesting that both dates are pretty much exactly a decade prior to the real-world release years. The prop people/script supervisor/director must have been proceeding on agreement to this rounded off timeline.