TC39 urges caution when using Stage 2-or below proposals, as it might result in inadvertent pressure from the community to keep the implementation as-is instead of improving it for fear of breaking existing code or ecosystem fragmentation (e.g. using a different symbol like # instead of @ for decorators).

The reasoning is that saying "ES7 Decorators" assumes that Decorators is expected to be in ES7. I mentioned this in my last post regarding compiling node_modules, but being in a particular Stage doesn't guarantee much: a proposal can stall, move backward, or get removed entirely.