The last time India and Australia played a series of four matches (or more) with no changes in captaincy on either side, the Aussies were still a largely all-conquering team and Clarke and Dhoni had just about established themselves as mainstays. The current series is the fourth full one since then (excluding the two match series in 2010) and a combination of injury, retirement, and suspensions has meant that each one has featured multiple leaders. And this time has been one better with changes on both sides. I can't remember when that happened last even in a series involving England :-) Going in, the expectation was that Dhoni would miss the first Test but captain for the rest and Haddin would stand in for Clarke for the full series. Two shocks of varying degrees in Hughes' tragic death and Dhoni's sudden retirement have turned that around on its head and its the future leaders (and currently the best batsman) on either side who're in charge heading into Sydney.