To adopt the microSD Express format, a CE manufacturer may need a controller/bridge IC, a card connector (aka socket), and test tools—bus analyzers, protocol analyzers, etc. AFAIK, the controller/bridge IC and test tools for SD Express should be compatible with microSD Express. Since there are already CE products in the market with an SD Express slot (e.g., MSI, Lenovo, and Asus), we may surmise that the supply and readiness of controller/bridge IC and test tools for SD Express, and by extension microSD Express, are not an issue.
That leaves the question of microSD Express connector’s availability. My quick search suggests that there are only three connectors advertised for sale currently:
Rego 9177MSD7-F00001
- Backward compatible with UHS-I cards
- Rated for PCIe 3; PCIe 4 compatibility unknown
- Rego revealed the product back in 2022. However, I can’t find any distributors stocking it, therefore it probably hasn’t been mass manufactured.
Amphenol 101019966912A
- Backward compatible with UHS-I cards
- Rated for PCIe 3; claimed to be PCIe 4 ready
- In stock at several distributors I checked; seems readily available
Amphenol 10102166A812A
- 3-in-1 connector, supporting UHS-I, UHS-II and Express (image source)
- Rated for PCIe 3; claimed to be PCIe 4 ready
- I only found two distributors have this in stock; doesn’t seem widely available
Looking at these, I think that if a CE manufacturer such as DJI/Nintendo/Valve would like to include a microSD Express slot on their products, there isn’t much obstacle. The other side of the chicken-and-egg equation is the card manufacturers. Samsung is now only “sampling” a microSD Express card. Will there be more?
In December 2023, the SD Association stated that Adata, Lexar, Phison, and SanDisk had adopted SD Express, but they did not specify whom among those will support the microSD Express format (
image source):
However, an Amphenol presentation slide indicated that the company was collaborating with SanDisk on the microSD Express connector. It doesn’t necessarily mean that SanDisk will release microSD Express cards, but they were at least planning to support it at one point (
image source):
The slides showing the card manufacturers has a link for Lexar, and if you follow it it's
their announcement from 2021, which was somewhat famous for the fact that they never actually brought the card to market.
The SanDisk one is a little bit more interesting, though, because it links to the SD Association's
verification program, which shows two SanDisk items in the SD Express list, one SD card and one microSD card (and no sign of the mythical Lexar cards). These were listed in December 2022, which is somewhat more recent, and the fact that they went through the verification program shows they actually exist (or exist
ed at some point). There are photos in
the PDF (see bottom right on the second page), and although the photo for the full-size SD card seems to be a mock-up, with "SD Express" in a plain font, the microSD card does actually look like it's using the proper branding, although it's very blurry. The full-size card also lists 800MB/s on it, so it's a PCIe 3 x1 card.
I wouldn't rule out the possibility that the SanDisk cards were anticipating a market that didn't exist, and just got shelved, as they were verified over a year ago and haven't been announced. However, as far as I'm aware WD/SanDisk only ever use in-house flash controllers for their products, and it's relatively unlikely they would have been willing to go to market with a line of SD Express products using the off-the-shelf Phison controller, which is their only other option. So it seems likely that they went as far as designing their own flash controller for SD Express cards, which is a relatively high level of investment.
The choice of expandable storage for Switch 2 likely would have been locked in by late 2022, so if it's using microSD Express, then SanDisk should have known about it by then. That they included a microSD card in the verification rather than just the full-sized SD card is also perhaps a clue that this was done with Nintendo in mind. A bit early, though, having cards ready 2 years before the console.
In any case it does suggest that, even if SanDisk were unaware of Nintendo's plans at the time they made these cards, if Switch 2 does use microSD Express then SanDisk should be able to spin up manufacturing pretty quickly, and we should get some competition between Samsung and SanDisk at launch, if not soon after.
Edit: Wait a sec. The PDF version of the verification list is a little old. The
web version includes two additional microSD Express cards added
today from ADATA, one 256GB and one 512GB. Hmm...
Second edit: A host controller chip from Realtek was also added today. This is a little bit notable as it seems to be a second-generation chip, with Realtek having verified an older model in 2022.