Just jumping in, but the value of mentioning the TV show in some way, like a post-credit scene, far outweighs the probable "negative".
In
some way, sure, it's possible. But the post-credits scenes would not be a good place to do that. And just tossing in an offhand "Hey, Coulson's alive" somewhere would be horrible, stupid, inept, self-destructive writing. Giving FitzSimmons or May a cameo somewhere, having Bobbi show up as a former agent, pitting Spider-Man against D'Onofrio's Wilson Fisk without specifically mentioning his
Daredevil backstory, those could work. But it has to be something that plays organically as part of the movies' universe, rather than a clumsy, distracting intrusion from the TV branch.
Say a million people go to the movie and see the scene and go to themselves " what was that?" In their heads. If they say anything outside of themselves, it would probably be to their friend in the seat next to them. And that friend will most likely say " I don't know" and then promptly forget about it. or, that friend might explain to them what Agents of Shield is about.
But it's only fifty thousand Agents of Shield fans tweeted or posted on Facebook about how excited they were about the tie-in, that would become a trending topic on social media and create lots of FREE positive Buzz.
I don't think confusing people with a
non sequitur that's only there to set up some extraneous plot point is going to generate
good buzz. I mean, that's what Thor's visions in
Age of Ultron were, a preview of coming attractions that didn't connect to the story being told, and that part is widely considered the weakest part of the film. And while there are plenty of parts of
Batman v Superman that were lambasted by critics and fans alike, one of the most universally panned bits was the scene where Wonder Woman watched video clips of the other superheroes who would show up in future movies, because it was just a random insertion that didn't connect meaningfully to the film itself. A story's first priority should always be its own internal needs. Hinting at something outside the story should only be done if it doesn't undermine or distract from the story itself.
and the post-credits scene is really for the hardcore fan anyway, who might be watching Agents of Shield already, or would then be excited to see the TV show
Again, if they already know about the show, then they don't
need to be informed of it. No way in hell would Marvel waste the valuable real estate of a post-credits scene for something so unnecessary. The movies make far more money than the shows, so they will always be the priority. And with the recent management split between Marvel's movie and TV divisions, the odds that the movies will ever incorporate anything from the shows have become even lower than they already were.