The real reason why de-dollarization is not happening fast is; although China is the largest trading partner to most muslim countries, its heavily skewed in Chinas favor because China still is heavily export oriented economy.
America otoh continues to buy a lot of goods from many muslim countries and provide millitary assistance to some key players.
I do agree that China needs to step up defense cooperation with the Arab world to move them away from the United states. Remember the Iran Saudi reconcilation is china effort to bring peace to the region. Once the Saudi sees Iran not as a military threat anymore then their need of United states military support will windle down.