If Boeing were to go ahead with its subsonic cruiser, and if it were to produce an economical, long range version, capable of flying LHR-SYD non-stop, I believe that it could have a dramatic effect on the market, particularly at the top end (ie business end) of the market, and could be quite appealing to QF.
As indicated in previous messages, a flight time of 16 hours, which would be nudging the outer limits of current non-stop flights, is quite feasible: current timetables show a total flying time from LHR to SYD via SIN of about 21.25hours (excluding the stopover); taking out the effect of the descent and takeoff, together with a straightening (shortening) of the flightpath that could be possible as there would be no need to fly directly over SIN, could possibly reduce this to about 20 hours. A further reduction of about 20%, due to the faster speed (as initially claimed by Boeing), could see this then drop to about 16 hours - a total savings of about 7 hours (including the stopover), or about 30%, on the current time.
This would mean arriving in SYD "1-3 hours after leaving LHR", depending on the seasons and daylight saving regimes:
LHR [+1] dp: 1800
SYD [+10] ar: 1900(+1)
Going the other way, flying time would be a bit longer (about 17 hours):
SYD [+10] dp: 1000
LHR [+1] ar: 1800
I believe that the savings in time, as well as the more favourable travel logistics that it would create, would be appealing to a fair section of the business market which would be prepared to pay a premium for such a service.
Indeed, the possibility of non-stop services from Australia to Europe, eliminating the need to go via SIN, was (and probably still is) one of the main motivations - perhaps the motivation - for SQ wanting to buy into AN, so that it too, indirectly, could offer such a service.
Other non-stop long haul possibilities for QF could be SYD-JFK, where the current flying time of about 20.50 hours (including the stopover at LAX) could be reduced to about 15 hours non-stop.