As you will have noticed, there are some gaps in the date.
你已经注意到数据有缺漏。
假如把主句改成过去式there were，其它不变，这句话对不对？
As you will havenoticed, there are some gaps in the date.
你已经注意到数据有缺漏。
这是will的推断性使用方法，如此讲可以讲得通，当然也大概是以后。
As you will havenoticed, there were some gaps in the date.
也行。
你应该已经注意到数据过去有缺漏。