It seems to just be a plan at the moment although like you say you can test it out:

https://vite.dev/guide/rolldown.html#how-to-try-rolldown

Nothing is keeping them to this plan other though, I hope they do follow through. That would make the graph on the page misleading in the other direction though as the speed feature would be included in the non plus version.

I want to also say I'm a happy vite user (and the other projects that team makes).

Nothing changes on VoidZero's commitment to open source. Vite 8 is still set to get Rolldown. I mentioned that also in my talks (e.g. https://youtu.be/fnyK-xXxVKU?t=3027)