There is https://github.com/pulumi/pulumi/issues/3622 tracking adding rust support. A number of community members have shown interest in doing work here.
The current languages supported are split between https://github.com/pulumi/pulumi/tree/master/sdk for the core Pulumi SDK of each language and the language runners, and https://github.com/pulumi/pulumi/tree/master/pkg/codegen for the SDK and program code generation.
While we have the concept of "language plugin" a number of features still assume that every language is statically known by the pulumi cli, and so any community language wouldn't work ideally right now. Having said that we have been chipping away at those limitations, and if there was a concerted effort from the community we could prioritise that work more.