Let’s also not forget that death isn’t always the end, especially in Marvel movies. Even if they stick to their guns and don’t pull soap opera-dramatic “he was alive all along” reveals, Marvel does love to jump around in time and play with their fancy de-aging software, something they’ve already done a couple of times with Douglas. We’ve seen 1980s Michael Douglas and 1970s Michael Douglas so far.
So much of Marvel’s storytelling is about how the past impacts the present. That’s a theme integral to Captain America’s character, for instance, and further solidified with “Avengers: Endgame” being all about important moments in the past.
The entirety of Phase 4 has been about the characters and the world reacting to the big events of the last two “Avengers” movies. They love to look back and have so far done so in a way that hasn’t cheapened any of the sacrifices the characters have made along the way.
Even if Hank Pym has a noble sacrifice in “Ant-Man 4,” they could still call him back for some good flashback stuff, especially since most of Hank Pym’s adventures as the first “Ant-Man” have gone untold. And don’t get me started on the multiverse possibilities. All we need is Dr. Strange to open up a sparkly window into another dimension if we want to get a nice little glimpse of our favorite grumpy old Ant-Man.