"Esperar que..." (to hope that...) can be followed by El Pretérito Perfecto del Subjuntivo to express the hope that something will have happened, as a completed action in the future.
Read and listen to these examples:
You will generally find a future reference in these sentences (unless it has been mentioned before and it is omitted.)
Future references in the examples above:
- "para entonces" (by then)
- "antes de la fecha acordada" (before the agreed date)
- "el lunes próximo" (next Monday)
The action that is hoped to have been finished/achieved is an action completed within that future reference.
For other uses of "esperar que..." see also:
- Using El Preterito Perfecto de Subjuntivo after esperar que to express a completed action in the past
- Using esperar que + El Presente de Subjuntivo to express hope