..who will pull the plug on their F-35 buy first...
Finnpog's description of the programme being a giant job creation scheme is, I think, uncomfortably close to the truth. F35 is so important to the US military/industrial heartbeat that it's too big to fail. And other countries have a finger in this pie too, so, to a lesser degree, have the same sort of motivation. If the programme survives and prospers as a commercial success, those governments want to be associated with that success, even if it is only a relatively small percentage of the whole. So, while the F35's trials and tribulations raise the fear of failure and spectre of additional cost which suggests they should get out, there is a counter-balancing fear of success if they do. Making a decision is therefore dangerous and most politicians will choose to do nothing if the opportunity presents itself. Once more, I support Finnpog's analysis that the military objectives of the people who eventually have to fly the plane into battle are probably not the most important issue for the continuation of the programme.
Now, if F35 were a Euro-consortium programme, it would have shaken itself to bits long ago. If the US were a customer rather than producer, it would have cancelled way back and made such a dent in the production numbers that the programme would crash anyway, assuming it came through the Euro-politics. But the way it is, with the US the biggest customer and manufacturer, it is likely to survive as a commercial programme, even if initial capability does not turn out to be what was expected. Capability will be developed over a long period. This happens with complex military programmes, but F35 will likely really push the boundaries at this stage as it pushed reliance on simulation and modelling too far at an earlier one.
The biggest threat to the programme is US cancellation, which is the fear that rattled export customers when the Pentagon slowed production down a couple of months ago. I think it would take a significant new technical issue for that to happen, an as yet unknown show-stopper. As far as any outsider can tell, this is unlikely. But only a complete collapse of capability is likely to deflect the US from continuing to support it's military manufacturing base. It would be a monumental dent in their credibility too, so further glitches will not be enough to derail the project, even if the accumulation of such problems erodes military capability.
Now, an export customer or two might cut and run, and this will impact pricing somewhat. LM will work hard to sell the dream to a new client fearful of being left behind or anxious to join the big boys, and this would take up the slack. Most, I think, will wait and see. Stay with the party for now and see how it looks in a few years time.
At present F35 excites public debate because times are hard, government spending is under scrutiny, there are technical challenges which put more pressure on price and delivery dates and a strong whiff of political incompetence and public service ineptitude wherever you look. So, F35 is a politically-driven programme for now. It will only become a military programme again several years into operational use, when upgrades and associated costs to make it work as required can be assimilated in smaller, more manageable phases. These will attract little attention outside military circles but will probably determine if it's the fighting machine everyone hoped for at the outset.