this is the latest update I've seen on this topic
Who knows if we will hear something soon. If the Saudis/emiratis want to be able to stand up to Israel, then they will have to start buying Chinese weapons. Can't see F-35s getting sold to them without giant compromises on their national security issues.
As for Iran, I think that until they take more strategic actions to aid China, you don't sell them anything more advanced. For example, China has been reluctant to even sell J-10Cs to Iran.
I just don't see Iran getting the FC-31.
1. Pakistan and Saudi are both Sunni countries with a long-standing relationship where part of the Pakistan military works for Saudi Arabia, and where Saudi provides funds to Pakistan. Saudi and UAE are also close allies in most respects.
2. Saudi, UAE and Pakistan all see China as a superpower which will one day eclipse the US in economic power, as per the surveys. Given time, that economic power will translate in military power.
3. China is Pakistan's most vital strategic partner in its rivalry with India
4. China is also the most important customer for the oil and gas produced by Saudi. Presumably this applies to UAE as well, but the numbers aren't readily available.
5. China is also the most important import partner for Saudi and UAE
6. Iran has nowhere near the financial clout of Saudi Arabia, nor the aerospace production capability of Pakistan.
7. Saudi and Iran have tense relations, and Saudi doesn't want China to turn to Iran. A FC-31 project involving Saudi and China would lock in a strategic partnership, probably involving Pakistan and UAE as well.
8. UAE has suspended a contract for 50 F-35s, so is weighing its options.
EDIT
9. China is at the forefront of solar and battery technology. Saudi is one of the best locations for solar as it has lots of desert and sun. Note that Saudi currently burns a lot of oil to produce electricity. But it's cheaper to generate cheap solar electricity (now at 1cent/KWh in Saudi) and sell that oil instead for a lot more money. Saudi and China both know that oil demand is going to decline in the long-term.