Above is an illustration of a country's concept of using distributed sensors to detect and target threats from stealth aircraft and also from attacking missiles. In this case the defending country is Japan, which sees possible threats from Russian and Chinese stealth aircraft and missiles from North Korea, Russia and China. (Diagram courtesy of Japanese defense agency ATLA)
Air Defense Networks
Infrared sensors, like other categories of a distributed air defense network, have some physical limitations. But it is the whole network including aerial, space and ground based radars (more broadly sensors, database, decisions and weapons) that makes for effectiveness.
Countermeasures against a defense network (such as knocking out nodes and releasing IR decoys/flares) my become less effective the more distributed the defending network becomes.
The main concern is the top "predators" Russia and China incrementally filling out the quality and quantity of sensors. An early success story for Russia and China was assisting North Vietnam to build its air defense system against the US - with most impact in that theatre in the 1960s-early 70s.
Anticipating the routes that an enemy's air armada may come from is of major importance. The armada can also include eg. stealthy Tomahawk range missiles, not only stealth fighter-bombers crossing borders.
Israel (in limited territory and the US (with Western allies aruably being global) have achieved over the last 30+ years have built deep air defense networks that Russia may want to re-emulate and China emulate.
Actual air defense campaigns also included offensive portions eg.
-Israeli versus Syrian Airforce, 1982 https://en.wikipedia.org/wiki/Operation_Mole_Cricket_19 and
- US+Allies, First Gulf War, 1991 https://en.wikipedia.org/wiki/Gulf_War#Air_campaign
Israel, US and main NATO allies heavily invested in air defensive/offensive technology from a high base.
Russia had high base expenditure, but it has problems maintaining the tempo of modernising the network. China has the money but is still building from a low base.
Problems of initial detection of F-35s/B-2/F-22s approaching and then database-decision making and passing to actual SAM or AAM targeting will force the Chinese to build a deep/intense network.
As China extends its militarisation into the South China Sea this may over-extend its air defences or deepen the network. Its hard to discern which trend.
Creeping F-35 Evolution
The software delays for the F-35 doesn’t diminish the severity of these delays. This is given getting software up to scratch is taking years. The dynamic of Russia working with China (and also perhaps Indian electronic know-how) to build sensor countermeasures against stealth (eg. F-35s) should not be under-estimated.
Radar Cross Section (RCS) materials were not such a delaying factor because they were demonstrably well understood on the F-22s by 2005 when the F-22s became operational.
Lockheed Martin (LM) trying to get all the F-35 features to work certainly contributes to the “too big to fail edifice” that LM has built for the US and foreign customers. The F-35, as the only new horse in the race on quality has an unlimited development budget beneficially yielding an unlimited revenue stream for LM. Good on LM :)
A President Clinton II is unlikely to alter this LM F-35 edifice but a President Trump might revisit The Deal and be more inquisitive.
What it means for Australia?
The evolution of the F-35 to acceptable standards may take so long that Australia's RAAF may need to buy another tranche of 24 Super Hornets. This is particularly in view of high usage of existing legacy Hornets and existing Super Hornets in the current air campaign over Iraq and Syria.
Australia may not buy all 72 F-35s intended or the 72 may be bought over an extended time (several decades). Australian defense officials, RAAF enthusiasts and politicians are of course deeply embarrassed they caved into LM and US Government pressure to put 100s of $millions of prepayments for the F-35s over a decade before these jets will be ready. Against this embarrassment is the jobs LM provides for retired senior officers - a recent example.
Australia's purchase of 12 Growler Super Hornet variants were to be most beneficial to "blind" an enemy while F-35s "snuck in" to bomb the enemy. But the Growlers will still be useful working with Super Hornet bombers, before the F-35s are ready.
A subsequent National Interest, article of Aug 18, 2016 “America's F-22 and F-35 Stealth Fighters vs. Russia's S-300, S-400 and S-500: Who Wins?” seems to come to the same conclusions.