Just how long can Apple run the table in the post-Jobs era? It was simply a matter of time before those whispers turned into a question asked out loud. George Colony, the CEO of Forrester, a research and advisory firm that has followed the company as closely as anyone, is taking a particularly dim view of Apple’s future. In a blog post that was guaranteed to spark a conversation, Colony says Apple’s days as a market leader are numbered; its “momentum¬†will carry it for 24-48 months” and then, absent a “charismatic leader” in the Jobs mold, it will devolve from “being a great company to being a good company.”