Rust-only means that there is no alternative C driver, and that the bulk of the logic (not the calls to kernel-wide abstractions) is implemented in Rust.
6.8 was released with a driver for https://www.asix.com.tw/en/product/EmbeddedEthernet/1-Port_Ethernet/AX88796B , but it's not consumer-grade hardware and the Rust driver is a duplicate of the C driver.
https://www.phoronix.com/news/Torvalds-On-Rust-Maintainers this and the below message from Torvalds' lieutenant bear directly on which release will have the first Rust-only driver for consumer-grade hardware, but seems to me they at least make "never" extremely unlikely, and probably push things up a bit.
An OpenGL 4.6-compliant driver for Apple M* GPUs exists out-of-tree. The author has this to say about it being mainlined:
> At the rate things are going, I wouldn't be surprised if upstreaming the drm/asahi driver isn't possible until 2026 at the earliest.
@Jono3h If the use of Rust in the kernel gets deprecated before any consumer-grade driver makes it in. Highly unlikely, but felt correct to add it.
If this resolves to a kernel version not yet listed, I'll add new vote entries. I'll also extend the resolution deadline as needed.