We know that there are 14 744s remaining with old first and BA's plan of record is to retire 9 744s by the end of 2015.
By April next year there will be 6 A380s in service so it is therefore possible that BA will have started to retire one or two 744s by then but we don't know what their latest plan is.
Depending on how the LAS route is doing, it is also possible BA may introduce a second daily flight from LHR using a 777 or they may drop the current flight to a 777 in which case you would have a better chance of NF. Any change they do make will come into effect in March so you could be lucky.