We'll be producing builds early next year. Those won't be anything we're recommending for production. Our goal is to have an early alpha in our own cloud environment by the end of Q1. I stress alpha. But we'll also have a bunch of tooling around it (which we've already built for the other parts of our cloud product) to backup data out of band, monitor it, shadow test it against production workloads, etc.
We're also building on top of the work of a bunch of others that have built Arrow and libraries within the Rust ecosystem.
When the open source GAs, I don't really know. But we're doing this out in the open so people can see, comment, and maybe even contribute. Who knows, maybe after a few years you'll be a convert ;)