LifeNavigator

The Future Perfect Continuous for assumptions about the present uses "will have been + [verb]-ing" to express a logical deduction about an ongoing activity happening right now, based on present evidence or general likelihood.

• They will have been working for hours by now, so they’re probably exhausted.
• Explanation: You assume they are currently in the middle of a long work session because it is late in the day.
• She will have been living in the city long enough to know all the shortcuts.
• Explanation: You infer her present familiarity with local routes based on the assumed duration of her stay.
• He will have been waiting outside for quite some time, judging from the look on his face.
• Explanation: Present visual evidence (his expression) leads you to deduce he has been standing outside up until now.
• The technicians will have been testing the system all morning, which explains the noise.
• Explanation: You account for the ongoing noise right now by assuming testing has been continuous throughout the morning.
• They will have been negotiating for days by now, which is why progress is slow.
• Explanation: The current slow pace leads you to assume that intense discussions have been dragging on continuously.