Well fred died so it can't be him. and Percy will NEVER be minister, i hope to the heavens, because otherwise the future of the magical world is doomed. plus he was seen working for hogwarts in the epilogue anyway, he clearly realised his fate was student control - like his prefect years - he had very little personality for a future so major.

i think kingsley would have remained minister for quite some time, probably even while harry and ron were parents, and they most likely worked as aurors, as dumbeldore lived for 130+ years, i do believe kingsley's abilities enable him to live up until this same memorable age. he remained a great great wizard for the whole duration of the books!
the only person i would like to see take over would be teddy lupin if he took in his mother and fathers footsteps of being great wizards - especially in the dark arts (which usually meant they were quite bright and intuitive!)