what became of sb/sth; what has become of sb.sth 和what will become of sb/sth.是习语,用来询问某人/某事 (遭遇)如何、(结果)怎么样等,不要去考虑其中的of是介词还是小品词。如:
What became of that student who used to live with you ?以前和你住在一起的那个学生后来怎么样了?I dread to think what will bacome of them if they lose their home. 我不敢设想他们如果无家可归将会怎么样。(例句摘自《牛津高阶英汉双解词典》第9版)