That said, ultra-long-haul is probably heading for the past, when taxation and corporate image become increasingly related to environmental impact and a very long haul aeroplane burns so much fuel just to tanker fuel, rather than multiple 1000-3000 mile legs, which from a carbon footprint viewpoint, look a lot less bad.
There will always be a point where the cost of tankering fuel exceeds the cost (including the extra cycle, deviation from direct path and no doubt a host of other things) of stopping to top up on the way. If two routes cross anywhere near the mid-point, then it could make sense to permit passengers to change from one route to the other there, potentially expanding the customer base and permitting the use of larger aircraft with lower seat-mile costs. press the concept a little further, bring other feeder routes to the tech stop point, and you have reinvented the hub and spoke system.