I'm not sure Anthropic even cares about "releasing" the next version. The rust one has been in use in Claude Code for more than a month now, used by millions of people, and that's as far as they probably really worry about it. They bought Bun for Claude Code and I doubt the open source project matters to them otherwise.
I very much doubt they would want to abandon the wider community. They do benefit from others using it.
To the contrary, I think any problem with this release would be jumped on harshly so they're being more careful than usual. There's not a rush for the community to move to 1.4 and any issues could poison the community trust.