The wikipedia article sometimes lists it as fediverse, sometimes not.
Are their any plans for matrix to join the fediverse?
The term fediverse is used ambiguously. Sometimes it refers to federated services in general but recently it is narrowed down to software that implements the ActivityPub protocol. Matrix however does not implement ActivityPub protocol and is therefore not part of the fediverse. In theory it would be possible for matrix servers to adopt ActivityPub but for the major implementations I don’t see that coming. Alternatively matrix bridges might allow some sort of interop.
While ActivityPub is a big player, the fedivierse is not limited to this particulat protocol. But rather to the interoperable network of protocols.
Fediverse includes: diaspora, Zot, ActivityPub, OStatus.
While not all instances would directly reach each others, there is a network effect between all of them.
That said, Matrix is not a protocol interoperable with any of the above, so not part of the fediverse. It could join the fediverse, however, if it implements ActivityPub for example, or at least a subset of it. For example, just publishing the username, picture and some kind of description or start chat button.
It’s part of the fediverse, but does not speak activity pub. So it won’t ever talk to mastodon, kbin, or Lemmy
