Actions in progress up to a future point: will have been + verb-ing
Subject + will have been + verb-ing
Subject + will not (won't) have been + verb-ing
Will + subject + have been + verb-ing?
💡 Combines future (will), perfect (have), and continuous (been + -ing).
✓By June, I will have been studying English for 2 years.
✗By June, I will study English for 2 years.
Duration up to future point needs perfect continuous.
✓She won't have been sleeping long when we arrive.
✗She won't be sleeping long when we arrive.
Duration before arrival needs perfect continuous.
✓How long will you have been living here by then?
✗How long will you live here by then?
Duration question needs perfect continuous.