If Ellsbury were signed to a five year deal he would only be 34 in his final year. I'm not really advocating signing him, but I would think there'd be just about as decent a chance he'd be a similar player in the fifth year as any other free agent signing. It's not like there are a lot of free agents around aged 29 or younger. I can't see signing him for 15 million a year regardless, though. I'd imagine he would go around 10-12 million a year.
"Respect was invented to cover the empty place where love should be."