In context, nothing within the MCU universe can compare to the ending of Infinity. It's dark and it's terrible for humanity. There are no movies set between the timeline of Avengers Infinity and Avengers 4, so she can't get time in another movie unless she is going to be integral to Avengers 4. (which to be fair, I was kind of hoping she would)… Maybe this will be Scott's chance to really shine and prove his worth, given we've to a degree spent a bit of time the last few pages pointing out that with The Wasp on the scene, what is the point Scott even having a suit? (in hindsight, why did Hank just not send his daughter in to Pym-Tech, other than so as to not break her cover)
The timing of mid and post credit scenes is often a little vague, but I'd say it was several months after the events of the movie. There would have been more than a few days pass between the events of AMatW and Infinity, and it's not like BP did anything more than lead an army and die in Infinity. He was probably the most underused hero of the entire movie.. It probably did kill the feel good buzz of the movie a bit killing off the Pyms, but Marvel Studios know how we wait for these scenes (even casual viewers finally get it, I don't think I've ever sat in a theatre so full when the lights came on), and MS know we want to know what's going on in the Universe post the finger snap..
