The 512Mb RAM die actually embedded into the same RP3A0 package as the CPU (it's the exact same CPU die used in the Raspberry Pi 3). So the stock is exactly the same world wide and linked. and I'm pretty sure the RP3A0 chips are packaged outside of China and would need to be shipped in for this.
Besides, China's RAM manufacturing is reasonably new, and only makes DDR4 and LPDDR4, not the older LPDDR2 which the RP3A0 uses.
But yes, they would have known LPDDR2 was EOL. It was EOLed 6 years ago, before they even launched the zero 2 (which they only introduced because the BCM2835 chip used by the original Zero was EOL), so it's not exactly clear why they are launching the CM0 now.
What makes the most sense to me is that they are currently developing a new chip, that will be a more-or-less drop in replacement for the RP3A0. If it's drop-in, then the design work on the CM0 won't be wasted.
Which would give us some clues on what the RP4x chip is, and it's current status (close enough that they know it will arrive before they run out of RP3A0 chips for the Pi Zero 2, but far enough away to bother launching the CM0 now, as long as the supply is limited).
This RP4x chip presumably needs to have low enough power/costs to fit the Pi Zero 3 budget (so quad Cortex-A725 cores?), while also using modern memory, LPDDR4 if not LPDDR5 to push the EOL out as far as possible. Since the Raspberry Pi 3 depends on the same EOL LPDDR2 memory, this theoretical RP4x chip will probably be used for a product refresh there too (and lowering their costs, as a bonus).
Problem is that I don't think LPDDR5 comes in any sizes smaller than 1GB, so if they want to stick to the current 512MB spec (and price point), LPDDR4 might be the way to go.
It might be nearer to EOL, but it's not actually EOL and should be fine for 5+ years after any EOL is announced.
Micron have EOLed a bunch of ddr4/lpddr4 parts, but that happens all the time, even to current nodes. There are still plenty of LPDDR4 parts in Micron's catalog [1] that are not EOL. TBH, I'm not exactly sure what the pattern is, maybe it's just parts on older nodes?
Reporters might be overreacting to product change notifications?
Also, it doesn't really matter when the first fabs start EOLing parts, it only matters when the last fab closes. And LPDDR4 might be a long-lived part, simply because China have opened a DDR4/LPDDR4 fab. Which might actually cause non-Chinese fabs to shut down DDR4/LPDDR4 early to focus on nodes with less competition.
Besides, China's RAM manufacturing is reasonably new, and only makes DDR4 and LPDDR4, not the older LPDDR2 which the RP3A0 uses.
But yes, they would have known LPDDR2 was EOL. It was EOLed 6 years ago, before they even launched the zero 2 (which they only introduced because the BCM2835 chip used by the original Zero was EOL), so it's not exactly clear why they are launching the CM0 now.
What makes the most sense to me is that they are currently developing a new chip, that will be a more-or-less drop in replacement for the RP3A0. If it's drop-in, then the design work on the CM0 won't be wasted.
Which would give us some clues on what the RP4x chip is, and it's current status (close enough that they know it will arrive before they run out of RP3A0 chips for the Pi Zero 2, but far enough away to bother launching the CM0 now, as long as the supply is limited).
This RP4x chip presumably needs to have low enough power/costs to fit the Pi Zero 3 budget (so quad Cortex-A725 cores?), while also using modern memory, LPDDR4 if not LPDDR5 to push the EOL out as far as possible. Since the Raspberry Pi 3 depends on the same EOL LPDDR2 memory, this theoretical RP4x chip will probably be used for a product refresh there too (and lowering their costs, as a bonus).