Although sales of both 757 and 767 are low, both have sold enough in the past to have paid for the tooling etc on the production line are are relatively cheapto produce, and will probably remain in production until they need the floor space for production of something new.
At the moment it is just a paper study; wheb designs are complete they will approach various airlines looking for a launch customer before formally adding it to its product list.
Deliveries for April consisted of 22 737s, 7 777s, 5 757s, 3 767s, 2 747s and 1 717. To cut costs Boeing are cutting 30,000 of its production staff; halving production rates.