待我长发及腰你已满脸胡渣
[dài wŏ zhăng fā jí yāo nĭ yĭ măn liăn hú zhā]
By the time my hair grows to my waist, your face will be full of stubble. It's poetically referring to the passage of time, possibly the evolution of the relationship status between two people over extended periods with a touch of irony or bittersweet observation.