> In addition, the fact that the loaded formatter doesn't appear to be RSpec 3 ready doesn't actually mean it's not ready -- consider that gems like fivemat and fuubar conditionally define the formatter class based on detection of what rspec version is running...so a warning issued here could be totally wrong (and thus confusing).

Given how the mechanism works, formatters have to register themselves if they're RSpec 3 ready, regardless of how they actually then supply an actual instance (this is what happened with Fivemat in the end) so that's less of a concern, but they might tell users to add specific formatter classes which would be more troublesome.

> Finally, we're telling users to "upgrade to 2.99, get warning free, then proceed to 3.0" -- but this deprecation doesn't fit in with that. There's no way to act on this deprecation while on 2.99 and solve it so that it is no longer issued. The `rspec-legacy_formatters` is intended for usage only in 3.0, right?

Adding the gem will be a no-op on 2.99 (just shuts this warning up).