Think you will find many carriers have used what we called a 're-dispatch' flight plan for eons. QF certainly used to operate without a destination alternate and that would be 13 hour sectors, SIN-LHR for example. In another company I have operated the B744 long haul on re-dispatch plans, flight plan to, say, FRA with the intended destination being LHR, when within an hour or so of FRA do a complete re calculation fuel remaining and in most cases, weather permitting, you have enough to continue to your originally intended destination. Can only think of one time en route SFO to HKG, strong head winds and a heavy load, had to drop into Narita, otherwise made it safely pretty much every other time in ten years of B744. This procedure is also known as using an en route alternate in some carriers.