This Index tracks HYG ETF, so What happens to that will help, if someone can explain. Thanks
According to the selection criteria in Section 2.3 of the iBoxx USD High Yield Developed Markets Index Guide
All bonds must have at the rebalancing day an expected remaining life of at least one year, and all new insertions must have an expected remaining life of at least one year and 6 months.
Since rebalancing happens once a month at month end, bonds are excluded from the Index at least eleven months before they mature. By the way, it's the ETF that tracks the Index, not the other way around. Hope this clarifies your question.