Okay, I'm with the staff on this one...
It's planned on a LHR-config 747-400. Chances of it being swapped are pretty minimal - things probably have to go quite badly wrong (like an aircraft to go badly tech, or get stuck in the US) for a swap to happen.
I'm sure the decision to swap it to a different aircraft type isn't a decision VS ops take lightly, as it will mean that the flight will need it's flight deck recrewing as a minimum, and there's the issue with the return sector - the return crew are already at the downline station, so a suitable return flight crew would have to be dead-headed in, somehow.
Chances are cabin crew numbers will need adjusting as well, as will the galley orders - the galley config differs between aircraft type, and even within the subfleets to some extent - therefore the caterer has to build the galley carts up dependant on the planned aircraft.
(So, for example, FAB/HOT/BIG have a fridge/freezer in their J galley, while WOW/ROC don't, and have space for more Atlas cabs instead - and no, I dont' work for VS. I'm just an observant geek with a bit of a photographic memory.)
Basically, it's a lot of hard work, and possibly a nightmare!
There's only 5 744s based at LHR now, and they are all the same from a passenger PoV - v:port, suites (with removeable dividers in the B-zone), "plastic horror" PE seats.
Cheers,
Mike