Aside from EgyptAir (which may sell off the 777s to simplify its fleet - they have small numbers of many different types) and Aeroflot (which also has only two 777s which are too big for most routes and expensive to lease), BA
has 5 777A variants which they are willing to sell (2 are out of service), UA
is considering disposing some of their 777s (various types available - UA
is currently looking at their 744 and 777 fleets in an attempt to cut costs - originally, it seemed that many of the 744s would go, but now some 744s have returned to service and 777s have been parked - UA
will keep the aircraft with favorable lease terms and dispose of those that are too expensive.)
Although the 777 has been in service for about 7 years, the second hand market is still rather small for the type.