I think the next Avengers movie should open with the team in the field facing whatever opposition, with Falcon-Cap directing the battle, already settled into the role. Just skip the "I'm not worthy" crap and get down to business.
What, after all, did Cap bring to the table for leadership? Strong tactical leadership in the field, and a strong moral compass. We've lost Cap, Natasha and Clint for tactical leaders. Winter Soldier may have the better tactical chops, but he's got way more personal baggage than Sam. Moral compass? I'm not sure they have anyone better suited than Falcon for that role.
As far as goal setting, long term planning and other big picture stuff, the team generally seems to handle those matters on a committee basis anyway.
Falcon seems to be a logical choice to replace Cap.
The question I have is when they're going to set "The Falcon and the Winter Soldier" TV show in the timeline and how it will affect the movies.