It would be funny if MCU was randomly destroyed by some kind of multiversal threat, like Infinity Ultron from What If.

Yea, that would be the way to end it. Everyone loses and the universes are destroyed.

That or Marvel Zombies spread to the multiverse.

There's only one proper epic way to end it:

Should have ended with Endgame. They're not really going anywhere with this and the individual movies are less self interesting than ever.

Wow that's a good question.

I don't want it to just fade away. That would feel wrong. You can't have grown men wailing in theaters when Cap picks up Mjolnir just to let an entire franchise go out in a whimper.

And I don't really want more multiversal shenanigans to be the big ending.

Maybe don't end it as in the whole thing is just...over. Change the focus to the X-Men for a while. Still the movie "616" (Earth-199999) but let the X-Men take over for 5 to 10 years. There's so much source material for the X-Men...then reintegrate other MCU heroes organically like the comics did during the zenith of the X-Men's popularity. Keep evolving.

The comic book 616 is still the main continuity for Marvel comics characters. Yes they've definitely had some multiversal shenanigans, but there's no reason to "end" it...just keep telling more stories.