not until 置于句首时，主句部分倒装。参见语法书籍
shall have done 属于将来完成时，与By the end of this year 对应。到今年末为止，表对将来的预测；
would have done是过去将来完成时，时间参照应是一般过去时态。如：He said he would have finished his task by the end of the month.
The performance ......应用前者： I had never seen......表过去的过去，即 过去完成时态