Based on the latest Kotlin Q&A session hosted by JetBrains around 30 people are part of the Kotlin team working on the language. At the time of this writing the official Kotlin GitHub repository has 145 contributors of which around 80% of the contributors are from the community (outside JetBrains). Plenty of interest in the repository with 7,538 stars. As @yole mentioned it would be easy to transfer Kotlin to the ASF (Apache Software Foundation) since the language is fully open source, is under the Apache 2 license, and provides an opportunity for the ASF to provide a programming language that works outside of the JVM. Oracle could make some moves that are against the interests of the Java platform community (eg unreasonable licensing) so having a Plan B is essential.
However there needs to be a reality check here. As mentioned above more of the community are involved in the development of Kotlin than JetBrains itself so community involvement isn’t an issue. ASF doesn’t have any relevant experience in managing a programming language, before taking on the management of Groovy. If you look at the success of Groovy over the last few years it has been shrinking under the ASF’s watch. Gradle Inc for instance is providing support for Kotlin to be used in writing build scripts, and many people anticipate that Gradle will eventually drop support for Groovy in the near future. Kotlin is currently in 12th position on GitHub in programming languages which is higher than Python (CPython), and C# (Roslyn), while Groovy is much further behind in 28th position (it has languished).
Some other companies/organisations have provided support for Kotlin like Gradle Inc as mentioned above. Pivotal (the one that used to manage Groovy, and is likely the biggest enterprise user of Kotlin) support Kotlin with Spring Boot, Spring Framework, and Reactor. Vert.x have recently provided Kotlin support. Square Inc are huge supporters of Kotlin on the Android side (eg SQLDelight). There will be plenty of other companies supporting Kotlin. @hhariri should seriously look at interviewing someone from Netflix (they maintain the Kotlin gradle plugin on Nebula) for the next Talking Kotlin podcast.