If you read the interviews it is clear that Whedon doesn't want to direct Avengers anymore. And Feige is giving another property to direct.
It's clear Joss wants to direct a superhero film with a female as the main character. I think they are giving Captain Marvel to Whedon.
That would give him plenty of rest.
In his interviews though, Whedon has lamented the fact he hasn't created anything original in 5 years. Captain Marvel may be a woman, and Whedon may be a feminist but that doesn't mean the two are a perfect, or even particularly good match. There are also rumours they are looking for a female director for CM.
There may be a curveball coming, but I think Whedon's done with heavy lifting for Marvel now. I'm sure he'll consult and offer opinions on things if they ask because him and Feige are good friends, but I seriously doubt he's lining up another property.