While I can't say the PrC being created by Paizo won't be leery power options, PrC do not have to be power option sets, depending on how they are designed. Though I myself am not generally a fan of PrC, all of my Kaidan faction supplements contain a few PrC.
In my Way of the Yakuza book, there is a prestige class for a Yakuza boss, who gets a few additional Sneak Attack progression, a set of unique arcane yakuza tattoos, a cut of the yakuza gang's income and some diplomacy enhancements as the leader of the red light district. While the tattoos are the coolest power feature, most of his abilities are 'flavor' based that fit a crime syndicate styled game, and of itself is not a mix of high powered features. They are options only.
In my soon to published Way of the Samurai there are two PrC options. One is a Bugyo, a samurai PrC with an emphasis on administration, diplomacy, tea ceremony, and scholarly talents versus a purely martial one - something like a court samurai. The other PrC is a Mosa, a frontline fighter with special talents for bodyguard duties, special challenge abilities (like samurai/cavalier), and DR.
Prestige classes don't have to be unbalanced power features. Mine are mostly flavor options for specific kinds of character concepts, with a few power enhancements for specific options only - corner case stuff in many cases.
I hope Paizo's PrC's are just as balanced and flavorful.
