Minato would have just further developed his abilities. He seemed to have a fascination with sealing techniques, which leads me to believe that he would have become even better with seals. He might have had time to further develop the Rasengan, and maybe even would have perfected it. He likely would have at least attempted to learn Sage Mode. He might not have been compatible, though. And his FTG would have probably become more versatile.
He would have been pretty busy as Hokage, though. On the other hand, he might not have had any time for any of the above things. He might have just maintained his skills.
On a side note, everything in the series would be completely different. Naruto wouldn't have been starting from scratch with everything. Assuming that Kushina still died, Naruto would have still been the best candidate for the next Jinchuriki. I assume that Minato had planned it all along after meeting Bee. Naruto would have had better control over everything, and I doubt his Jinchuriki status wouldn't have been a secret. Minato would have also taught Naruto most of his techniques, and by the Chunin Exams, he would have been more on par with Sasuke in terms of skill (as opposed to his usual determination). It would have been like Goku and Gohan from DBZ. I don't think Minato would have killed off the Uchiha. Orochimaru wouldn't have had a reason to attack the Leaf Village. Sarutobi would have just died of old age.