It refers to the new CLI, i.e. the "nix" command. The old CLI is the nix-* commands (nix-env, nix-store, etc.). The new CLI and flakes are still marked experimental, but the plan is to stabilize them and call that "3.0". So it won't be very different from the current 2.12 - you just won't need to enable some experimental features anymore to get the new CLI/flakes.
the_duke|3 years ago
I've been using flakes for well over a year and there doesn't seem to be much discernible progress.
Macha|3 years ago
There is agreement in principle to carve out a store only Nix so the no-flakes crowd can build their own UI on it which is held by them as a pre-requisite to any stabilisation of flakes, along with some bad blood of it being announced by blog post. But it's slow because the project maintainer and chief flakes advocate doesn't want to adjust the project just so an alternative frontend specifically to avoid their view of an easier Nix should go ahead.
People are still working somewhat constructively towards this in 134, but because their goals feel fundamentally opposed, it seems likely to go on a while.