With an equal amount of Mid-J and Super Hi-J aircraft now in the fleet (18 each), you would expect things to remain reasonably steady, especially at this late stage. However, unless you're on the JFK route, most routes are open to a late downgrade substitution due to aircraft availability (aircraft going tech) and bookings and looking at your flight, with a lot of seats still available for sale, unless things change dramatically BA could sub a Mid-J in on Monday without much inconvenience to any CW pax.

BA 192 0
DFW 05/22/17 6:25 PM
LHR 05/23/17 9:20 AM
744
F9 A8 J9 C9 D9 R9 I0 W6 E4 T0 Y4 B3 H0 K0 M0 L0 V0 S0 N0 Q0 O0 G0

While you should be on a Super Hi-J on your flight, you really won't be certain until you step onboard (or look at what plane is operating the outbound LHR>DFW sector on Monday).

Safe travels!

Pilot37