Scala 2.13.0-RC2 is now on Maven Central.
We are currently working on writing release notes, publishing modules, and so forth.
Gory details at https://github.com/scala/scala-dev/issues/626 . We’ll also update this thread as things progress.
As usual with prereleases, RC1 and RC2 are not binary compatible, so the ecosystem will need to re-publish.
RC2 draft release notes: https://gist.github.com/SethTisue/d774067a3028e5665c0aa9e9cadb55aa
libraries for RC2 are starting to show up at https://github.com/scala/make-release-notes/blob/2.13.x/projects-2.13.md
Scala.js 0.6.27 and 1.0.0-M7 are already published for Scala 2.13.0-RC2.
shapeless 2.3.3 published for 2.13.0-RC2 just now.
published for RC2: scala-collection-compat, scala-parallel-collections, scala-parser-combinators, scala-xml, scala-java8-compat, scala-swing, scala-js
and: scalacheck, scalatest (3.1 only at the moment), scalaprops
and and: shapeless, silencer, genjavadoc, kind-projector, wartremover, scalaz, …
not yet: specs2, cats, …
macro-compat 1.1.1 published for 2.13.0-RC2 just now.
more libraries over the RC2 finish line: specs2, scalatest 3.0.x (previously only 3.1.x was available), akka & akka-http, spray-json, sconfig, scallop, airframe, scoverage, expecty, …
I don’t want to jinx it, but: so far there is no issue that would require an RC3.
Well, there was one API change that we considered important enough to do an RC3 for: https://github.com/scala/scala/pull/8083. We merged a total of 16 PRs for this 
final candidate:
https://github.com/scala/scala/pulls?q=is%3Apr+milestone%3A2.13.0-RC3+is%3Aclosed
As always, we’re conscious of balancing the efforts required of library maintainers in building for new RCs (thank you!) with allowing ourselves enough RCs to get the final release right (because our next opportunity to make binary breaking changes is in 2 years!)
I feel confident we’ve now converged, and hope to get the 2.13.0 final out before Scala Days! 
We’re working hard to release RC3 today (or at the latest by the end of the week). Currently following up on the changes needed to get the community build to the same number of green projects as RC2.
More details at https://github.com/scala/scala-dev/issues/628.
RC3 jars are on Maven Central
Scala.js 0.6.28 and 1.0.0-M8 built for 2.13.0-RC3 are on their way to Maven Central.
https://github.com/scala/make-release-notes/blob/2.13.x/projects-2.13.md has been refreshed for RC3
if y’all are curious what the initial stages of ecosystem publishing look like, I’ve now documented in the initial dependency chains here: https://github.com/scala/scala-dev/issues/629
now available for RC3:
still pending: kind-projector, shapeless, scalatest, scala-collection-compat, specs2, …
shapeless 2.3.3 for now published for Scala 2.13.0-RC3.
newly available: kind-projector, specs2, shapeless, scalatest 3.0.x, scala-collection-compat, silencer, nscala-time, airframe, hedgehog, jsoniter-scala, expecty, …
pending: ScalaTest 3.1.x, akka, cats, …
this is enough to announce with, so I expect we’ll announce today
ScalaTest 3.1.0-SNAP12 is out 
(alongside 3.0.8-RC5)
other recently published libraries: discipline, claimant, refined, scallop, wartremover, …
cats and akka are actively progressing towards releases.
more libraries for RC3: