America's next conflict: role of the Marines?

I'm curious what the role of the Marine Corps will be in America's next (inevitable) conflict. They have expressed interest (and a need) to return to amphibious roots, after being 400 miles from the coast in Afghanistan for the last 9 years or so. But I feel like no matter where the war is, the Marine Corps will still be used like they are being used today: a second army. Thoughts?