After reading around different threads and the most recent chapter I have come to a conclusion. Sai is being used as a plot device. Through imitating and dissing Sasuke and insulting Naruto and Sakura, I believe Kishimoto is using Sai to heal the old wounds between Sasutards and Narutards over the Sasuke v. Naruto fight. Sai is a common enemy to both characters. To Naruto he is an untrusting and perverted (in a homoerotic way) dick who is insulting people. To Sasuke he is a future enemy as he sees Sasuke as a traitor and upon meeting will most likely seek to destroy Sasuke. Through unprejudiced disrespecting, in my opinion, Kishimoto has produced a disposable character for the purpose of cushoning Sasuke's inevitable and hopefully speedy return and forwarding the distrust at home sub-plot.