This issue is not really about the range of the aircraft. The two main problems are economics and the human factor.
Ultra long hauls are very difficult to operate from an economics perspective. The reason for this is that the plane needs to carry tons of fuel for a very long time. It is much cheaper to land and re-fuel. This is the reason why some of those long flights (SIN-EWR) have gone all business class. It is just not financially viable. And if fuel prices would rise further then this would expose the company to a huge risk.
And of course a 20 hour flight is nothing you really want to experience in a 10 abreast 777. So nobody wants to be stuck in a plane for such a long time.
Luckily non of the most profitable airlines in the world operate any 777.

Because QF and CX really don't like each other? QF would rather codeshare with EK than get into bed with CX.

Yeah, I know that the weight of the fuel becomes a real problem on ultra long flights. CX doesn't seem to have any problem filling up the HKG/JFK nonstops, though, and in all cabins. I would have thought that there'd be a fair amount of premium cabin demand for a LHR-SYD nonstop, though. Completely agree, 20 hours in Y isn't for me, regardless of the aircraft type. OTOH, I'll happily take 20 hours, even more, in the F cabins of several carriers.

Last I checked both EK and SQ operate lots of 777s.

Back to the OP's question, QF and CX compete on both kangaroo route and Australia to Asia.

Codeshares work better when they are complementary not competitors.

At least QF has indirectly acknowledged some deficiencies in its Perth international schedules. Tickets to/from PER to HKG and NRT now will routinely permit connections in SIN to CX / JL flights to those destinations respectively. But I do note that to HKG codeshare (ie QF numbers on CX flights) flight numbers are not used, which makes for interesting FF assignments (to AA program) because of the difference in mileage credits on QF/CX flight numbers.

I can only hope that BA will offer AA codeshare numbers SIN-LHR.

Fred

Both EK and SQ don't even have a credit rating as they are government owned. AFAIK the only airlines in the world with an investment grade credit rating are Southwest, Qantas and Lufthansa.

Your previous post referred to profits not credit ratings.

As there is so much competition on these routes, I don't believe a tie up between CX and QF would necessarily be turned down by the competition authorities in either jurisdiction. There would inevitably have to be some concessions, however I can't see that stopping further cooperation or even merging.

Please bear in mind that I was referring to HKG-AUS, not the entire Kangaroo Route. AFAIK, the only non-CX/QF direct flights between the two regions is VS's HKG-SYD FLT. Please correct me if I am wrong.

Nonetheless, even though I was only talking about the HKG-AUS part, if a code-share is not possible on these routes, I don't see a joint-venture between CX and QF on the entire Kangaroo routes possible, either. They can certainly keep the code-share to FCO and perhaps expand that other non-UK destinations, but definately not LHR.

Very True, their only main competitor would be SQ for the kangaroo route if they did a joint venture. Then SQ would probably demand the US-Australia routes they wanted to do years ago as some type of settlement for increasing competition on Australia routes.

They also have competition on the kangaroo route from MH and the middle eastern airlines.