Keep in mind, this applies to ODI's and T20's.
It's all in the title, how many years will it take for Afghanistan Cricket Team to reach a level where they can challenge all top ranked sides even though they wont be the best.
Like West Indies or New Zealand who are ranked much lower on the table but they can beat the top 4 on any given day. Currently, I don't really see any good players in their team other than Hamid Hassan and Mohammad Nabi.