One other possible source of B763(ER)s might be from Thomson, who recently furloughed 137 pilots and that equates to a large number of planes sitting on the ground. So far they have only reduced their fleet by 1 x A321. Their fleet includes 13 B763(ER)s.
and that equates to a large number of planes sitting on the ground
Wrong
It means the remaining pilots will be working more often.