Nope, being worked on rn, expect an update soon!

The Comfy Stability-API nodes are now included out of the box in Swarm (https://github.com/Stability-AI/ComfyUI-SAI_API)

So you can use a "Stability SD3" node to generate using SD3 in comfy.

There's a handler under "user" that handles API keys easily for you:

(Only applies to usage in Generate or Simple tab, requires you add an input with id api_key_override)

And here's a workflow that hooks up SD3 text-to-image as a simple interface (compatible with the Simple tab currently hidden under the "Experimental" server setting, but also can be used in the generate tab)
sd3.json

Here's an image2image one too:
sd3img2img.json

Are we going to get functionality that allows us to simply change
https://api.stability.ai/v1 to https://api.stability.ai/v2beta in the Backend config for StabilityAPI?

Not sure what'll happen with the StabilityAPI backend atm - either will be scrapped (in favor of the comfy node setup) or rewritten entirely. Right now it's designed for the much more predictable/static v1 API, whereas the v2 API is more of a series of completely distinct APIs joined together, ie it needs unique handling for each end point.