I already consider Subban to be one of the most mature guys on the team, all he needs is the experience and he'd make a fine captain. Gorges is next in line, but once he's shipped out (not saying it's imminent, but switching teams is not unheard of for non-core players) Subban should be in the running.
And Prust? No thanks... Can you imagine Jean Beliveau calling an opposing coach a bug-eyed, fat walrus? It was funny, but there's a certain amount of dignity that should come with the title.
People overrate who wears the C so much it's not even funny. Good teams have 8-10 good leaders and they don't wear the C...or an A for that matter.
Plus, Gionta is an excellent captain so not sure why people keep bringing up "player X should be captain".