MCU Phase 4: 8 Reasons Why It Must Look To The Past
6. Heroes From A Different Time
Although convincing Chris Evans to reprise his role as Captain America for another film - let alone a World War II spin-off - seems fairly unlikely to happen, it's clear that Marvel aren't quite done with the license yet.
Sebastian Stan's Bucky is very obviously being set-up to takeover as Cap come Avengers 4, and while we're not talking about the future just yet, it's important that Marvel are still invested in the Cap brand. Not in the sense that it proves more films are on the way, but because there'll be an awareness of the character's history; the WWII book doesn't end with The First Avenger.
On top of Cap's ties to the Howling Commandos, in the comics, Steve Rogers actually led a group called 'The Invaders'. Together with Namor and the first Human Torch (whose android body we actually saw in the first Cap film), Cap went to war and the first modern superhero team was created. One thing that's important to remember, however, is that Steve Rogers isn't integral to the Invaders' makeup - you could easily replace him with, say, a relative of Nick Fury, or any of the Howling Commandos for that matter.
Marvel have had issues with bringing Namor to the big-screen for a while now, but if they were to go all-in with another World War feature, it'd be the perfect way to introduce the character. If there's potential to make him a full-time Avenger, then even better.