Whether or not Steve Smith will become a great as a captain is secondary. How long will he remain captain is the primary question.
The 25-year-old has a good horoscope with Planet 'X' in deepest exaltation. This has enabled him to be a consistent player and also captain Australia. But his horoscope doesn't promise greatness as there are no more planets to add to the might of Planet 'X'. In all probability, Michael Clarke will come back and take over the reins.
Clarke will be around for a year or two. He will then make way for Smith.
Also expect David Warner to assume the top role in ODI cricket. Soon, Australia will have three different captains and 'Smithy' will get to lead the Test side. His personal planets are in the resolute Taurus and ambitious Aries. Expect him to show maturity and aggression. He will win a few Test series as captain, but will fall short of greatness as he may find it difficult to win an away Ashes series. He could also also face defeats in India and South Africa.