I suspect that 16GB RAM is very much on the table for the successor, and would feel (quietly) confident about that. 12GB is the cellar of expectation, and I don't see it being lower than that. 8GB is too conservative, given what we know about the rest of the SoC, about developer feedback, etc., and it won't be enough, unless they want to sell a product destined to fail. Some flagship phones have had 12GB since 2019, then gaming phones have had 16GB.
18GB is a thing, even - that's been in production since March 2021, and it will have been for
at least two years by the time the next platform arrives. In fact, earlier this year, the
OnePlus 10T 5G was confirmed to have 16GB, and it won't be long before more flagship phones follow. Steam Deck, with its weaker SoC, has 16GB. Steam Deck isn't going to sell anywhere near what a Switch has. I would be very surprised if it reached Wii U sales. So, the reasoning follows that Nintendo can have 16GB at a better rate, as they're expected to sell more hardware.
BTW, in the Samsung Galxy Note 20 Ultra's BoM from 2020, 12GB LPDDR5 RAM with 128GB UFS 3.0 was $61.50. One imagines such a bundle with 16GB might be similar to that now. Still, if 16GB is in the devkits, why not? 4GB was in the Switch devkits and in the launch product. At the time, 4GB was the standard in flagship phones, but it's also true that the PS4 was going to go with 4GB RAM until the last minute, until developers said more is needed. I suspect it will be 16GB because some phones are already there, SD is there, and developer feedback suggests that they'll go for it. The confidence is there, too. Also,
16GB LPDDR5 RAM has been in production for over two years, with gains over the 12GB in bandwidth, efficiency, battery life, and performance.