Just booked an LHR-ORD flight on a 763 at the end of July for me and Mrs 1P, and when I upgraded discovered they were lie-flat C seats.... ^^^ The other thread about the roll-out of these seats doesn't seem to have any definite data on when and where they're being introduced beyond the original IAD-FRA and IAD-SFO routes. Unless I've missed another thread somewhere....
All seat maps for 747s and 767s on the IAD-FRA routes (and some others) show the new seat configuration, but that's no guarantee that a new-configuration aircraft will actually fly on your flight.